Visualization VocabularyDataviz vocabulary

3D chart

Chart whose marks are rendered as volumes although the third dimension encodes no data.

chart, critique

abstraction

Restating a concrete problem in terms of data and task types.

process

accessibility

Design allowing use by people with varied abilities.

process

accuracy

Closeness of a measurement to the true value.

statistics

adjacency matrix

Square matrix encoding the presence of links between nodes.

chart, matrices and tables

aesthetic

Mapping of a variable to a graphical attribute in the grammar of graphics.

encoding

affective objective

Learning objective about an attitude or value of the viewer rather than about a fact.

process

aggregation

Summarizing several observations into a single value.

data

alignment

Matching of the edges of elements.

typography

alluvial diagram

Blocks stacked at each stage of an ordered sequence, linked from one stage to the next by bands whose width encodes the count moving from one group to another.

chart, flows

alluvial plot

Gapless stacked blocks at each stage of an ordered sequence, crossed by ribbons that each follow the same group of units from the first stage to the last; the height of a column gives the count at that stage.

chart, flows

alpha

Degree of transparency of a mark.

encoding

alt text

Textual description of a figure for screen readers.

process

angle

Opening of a sector encoding a quantity.

encoding

animated transition

Continuous movement of marks between two states to preserve tracking.

interaction

image: Wikimedia Commons, Eadweard Muybridge, Public domain

animation

Time transition between successive states of a view.

interaction

annotation

Text or stroke added to point out something notable.

encoding

annotation layer

Set of explanatory elements layered over the representation.

encoding

image: Wikimedia Commons, voir Wikimedia Commons, GPL

Anscombe's quartet

Four datasets with identical statistics but very different shapes.

statistics

anti-objective

Conclusion the viewer should not draw from the visualization.

process

apophenia

Perception of structure in purely random data.

critique

arbitrary threshold

Cutoff picked without justification and used as the yardstick for a phenomenon.

critique

arc diagram

Nodes on a line joined by arcs.

chart, networks and trees

area

Area of a mark encoding a quantity.

encoding

area as quantity

Value encoded by the radius of a shape rather than by its area.

critique

area chart

Line chart with the area under the line filled in.

chart, lines and areas

arrangement

Layout of the elements within a mark used as a visual variable.

encoding

aspect ratio

Ratio of width to height of the plotting area.

encoding

assistive technology

Hardware or software compensating for an impairment to access content.

process

associativity

Property of a visual variable leaving categories equally visible.

perception

atlas

Organized collection of maps covering a territory or a theme.

map

attention

The gaze selecting one part of the scene at the expense of the rest.

perception

audience

Intended group of recipients for the visualization.

process

axis

Graduated line materializing a scale.

encoding

axis label

Text naming the variable carried by an axis and its unit.

encoding

banding

Spurious visible boundaries in a continuous gradient.

critique

banking to 45 degrees

Choosing the aspect ratio so average slopes sit near 45 degrees.

encoding

bar chart

Bars whose length encodes a quantity compared across categories.

chart, bars

barcode plot

Every value drawn as a thin tick on a single axis.

chart, points and bubbles

baseline

Reference value from which marks start.

encoding

bean plot

Mirrored density in which each observation is a short line, and the group mean a longer one.

chart, boxes and densities

beeswarm plot

Non-overlapping offset points revealing local density.

chart, points and bubbles

image: Wikimedia Commons, Martin Hilbert, Priscila López, CC BY-SA 3.0

big data

Data too large or too fast for conventional tools.

data

bin

Interval of grouped values.

encoding

binning

Splitting a continuous variable into intervals.

encoding

bipartite network

Network whose nodes form two sets with every link joining one node from each set.

chart, networks and trees

biplot

Simultaneous projection of individuals and variables of an ordination.

chart, points and bubbles

bivariate map

Map that crosses two variables in a single color legend.

map, maps

Bland-Altman plot

Difference between two measurements against their mean.

chart, points and bubbles

block diagram

Diagram of a system in which each component is a box and each exchange a line or arrow between boxes, with no internal detail.

figure, non-chart figures

bootstrap

Uncertainty estimated by repeated draws from the sample.

statistics

box plot

Distribution summary using median, quartiles and extremes.

chart, boxes and densities

branch support

Value borne by a branch measuring confidence in the grouping.

encoding

brief

Document framing the request, objectives and constraints.

process

brushing

Direct selection of a subset of marks.

interaction

brushing and linking (interaction)

Propagation of a selection to all coordinated views.

interaction

bubble chart

Scatterplot where size encodes a third variable.

chart, points and bubbles

bullet graph

Single bar compared to a target and reference bands.

chart, bars

bump chart

Change in rank of several entities over time.

chart, lines and areas

calendar heatmap

Calendar grid where each day is colored by a value.

chart, matrices and tables

calligram

Text laid out so as to draw a figure related to its meaning.

figure

callout

Annotation linked to a precise point by a line.

encoding

candlestick chart

Mark encoding open, close, low and high over a period.

chart, bars

caption

Text under the figure identifying and explaining it.

process

Cartesian coordinates

Frame with perpendicular axes.

encoding

cartogram

Map whose areas are distorted in proportion to a variable.

map, maps

cartographic generalization

Simplification of a map by selecting, smoothing, aggregating or displacing features to suit its scale and purpose.

map

image: Wikimedia Commons, Johannes Kepler, Public domain

cartography

Art and technique of designing and reading maps.

map

categorical data

Data whose values are unordered categories.

data

category

“Identifiable part of a component or of a variable” (Bertin, translated).

data

causal inference

Cause-and-effect link read into a chart without the data establishing it.

critique

central tendency

Typical value around which data cluster, such as the mean, median or mode.

statistics

image: Wikimedia Commons, Globe_and_high_court.jpg: created by jjron Globe_and_high_court_fix.jpg: created by jjron, edited by Fir0002 derivative work: WikiCantona (talk), CC BY-SA 3.0

change blindness

Failure to notice a visual change between two views.

perception

channel

Graphical attribute of a mark that encodes a value.

encoding

channel ranking

Ordering of visual channels by how accurately readers decode them for a given attribute type and task.

encoding

chart

Visual representation of data through positioned marks and graphical attributes.

chart

chart chooser

Decision tree leading from the need to the chart type.

process

chart type

Established combination of marks, attributes and layout that goes by a name of its own.

encoding

Chartability

Set of heuristics for auditing the accessibility of a data visualization.

process

chartjunk

Graphical ornament that carries no information.

critique

Chernoff faces

Multivariate display in which each variable drives one feature of a drawn human face.

chart, glyphs

cherry-picking

Choosing the data or period that supports the desired conclusion.

critique

chord diagram

Relationships between entities placed around a circle.

chart, flows

choropleth map

Map whose areas are colored by a relative value.

map, maps

circle packing

Hierarchy shown as nested circles.

chart, sectors, tilings and units

Circos plot

Relationships between genomic regions arranged around a circle.

chart, radial

Cleveland dot plot

Dots positioned on a shared axis against categories.

chart, bars

Cleveland-McGill hierarchy

Ranking of encodings by reading accuracy with position first.

perception

closure

The eye completes incomplete shapes.

perception

clustering

Grouping of observations into classes that are not set in advance.

statistics

coefficient plot

Model coefficients and their intervals aligned on a common axis.

chart, points and bubbles

cognitive load

Mental effort demanded by reading a representation.

perception

combination chart

Two mark types overlaid in the same coordinate system.

chart, composites

common fate

Elements moving together are perceived as a group.

perception

compact letter display

Letters shared by the groups a test cannot tell apart.

encoding

component

Variable of the information transcribed in the graphic.

encoding

composite figure

Figure gathering several panels under one caption and one number.

process

compromise projection

Projection that preserves neither angles nor areas but limits both distortions.

map

cone of uncertainty

Cone-shaped area around the forecast track of a hurricane showing uncertainty about the position of its center.

encoding

confection

Assembly of visual events drawn from various sources and juxtaposed to carry an argument.

chart, non-chart figures

confidence band

Area framing a fitted curve and showing the uncertainty of the fit.

encoding

confidence interval

Interval expected to contain the parameter at a given rate.

statistics

confirmation bias

Tendency to retain only what confirms the expectation.

critique

conformal projection

Projection preserving angles, and thus local shape, while distorting areas.

map

confusion matrix

Table crossing the observed classes with the classes predicted by a model.

statistics

connected scatterplot

Scatterplot whose points are joined in time order.

chart, points and bubbles

consistency

Using the same encoding for the same quantity across a series of figures.

process

continuity

The eye follows the smoothest paths.

perception

continuous variable

Variable that can take any value in an interval.

data

contour map

Lines joining points of equal value.

map, maps

image: Wikimedia Commons, Fede Threepwood, Public domain

convex hull

Smallest convex polygon containing a set of points.

encoding

coordinate system

Geometric frame that places the marks.

encoding

coordinated multiple views

Several views of one dataset reacting together.

interaction

image: Wikimedia Commons, DenisBoigelot, original uploader was Imagecreator, CC0

correlation

Measure of the presence and the extent of a mutual relationship between two variables.

statistics

correlation coefficient

Normalized measure of association between two variables.

statistics

correlogram

Autocorrelation of a series plotted against the lag.

chart, lines and areas

corrgram

Colored matrix of correlation coefficients between every pair of variables.

chart, matrices and tables

count

Number of observations in a category.

data

covariation

“The tendency for the values of two or more variables to vary together in a related way”

statistics

crispness

Degree of blur of the edges and fill of a mark.

encoding

cross-filtering

Filter applied in one view that restricts all the others.

interaction

curvature

Degree of bending of a line mark encoding a magnitude.

encoding

cycle plot

Time series split by phase of the cycle to separate trend from seasonality.

chart, lines and areas

dashboard

Set of summary views monitored over time.

process

dasymetric map

“A technique in which attribute data that is organized by a large or arbitrary area unit is more accurately distributed within that unit by the overlay of geographic boundaries that exclude, restrict, or confine the attribute in question.”

map, maps

data art

Artwork using data as its material.

process

data cleaning

Correction of errors, duplicates and inconsistencies.

process

data density

Amount of information displayed per unit of area.

critique

data journalism

Journalism grounded in the analysis and display of data.

process

data physicalization

Physical artifact whose geometry or material encodes data.

encoding

data provenance

Documented history of the transformations applied to the data.

data

image: Wikimedia Commons, Максим Пе, CC BY-SA 4.0

data science

Field combining statistics, computing and an application domain.

process

data source

Declared origin of the data used.

data

data storytelling

Building a narrative that guides the reader through the data.

process

data table

Presentation of exact values in rows and columns.

chart, matrices and tables

data validity issues

Data quality flaw ignored or wrongly invoked to support a conclusion.

critique

data visualization

Graphical representation of data meant to reveal its structure.

process

data wrangling

Shaping data before analysis or visualization.

process

data-ink ratio

Share of ink devoted to information out of total ink.

critique

dataset

Structured set of observations and variables.

data

decision tree

Tree that chains choices and uncertain events, from the root to the leaves, up to the possible outcomes of each path.

chart, networks and trees

decoding

Process by which a reader recovers a value from the chart.

encoding

dendrogram

Tree showing a hierarchical classification.

chart, networks and trees

density plot

Smoothed estimate of a continuous variable's distribution.

chart, lines and areas

dependent variable

Variable whose values change according to the independent variable.

data

depth

Position of a mark along the viewing axis of a three-dimensional scene.

encoding

depth perception

Ability to judge the distance and relief of objects from visual cues.

perception

descriptive statistics

Methods that summarize and describe data with summary measures, tables and graphs.

statistics

design critique

Collective review of a figure before publication.

process

details on demand (interaction)

Detail shown only when the reader asks for it.

interaction

detrending

Removing the long-term trend of a time series to bring out its deviations.

statistics

developable surface

Surface (plane, cylinder or cone) that unrolls flat without distortion and onto which the globe is projected.

map

diagonalization

Reordering the rows and columns of a matrix until its structure appears.

process

diagram

Construction in which “the correspondences in the plane can be established between all the elements of one component and all the elements of another component” (Bertin, translated).

chart

dimension reduction

Projection of data with many correlated variables onto a few key dimensions.

statistics

image: Wikimedia Commons, NerdBoy1392, CC BY-SA 3.0

dimensionality

Number of variables describing each observation.

data

direct labeling

Series name placed on the series itself rather than in a legend.

encoding

discrete variable

Variable taking only countably many values.

data

dissociative variable

Visual variable that changes the visibility of signs and prevents perceiving them all equally.

encoding

distortion (interaction)

Enlarging part of the view at the expense of the rest which stays visible.

interaction

distribution

Spread of counts over the possible values.

statistics

diverging bar chart

Bars running up or down from a reference line according to sign.

chart, bars

diverging stacked bar chart

Stacked bars whose segments extend either side of a baseline.

chart, bars

donut chart

Pie chart with a hole in the middle.

chart, sectors, tilings and units

Dorling cartogram

Cartogram where each unit becomes a proportional circle.

map, maps

dose-response curve

Curve of the measured response as a function of the administered dose.

chart, lines and areas

dot density map

Scattered dots whose count encodes a total.

map, maps

dot plot

Distribution in which each observation is a dot stacked above its value.

chart, points and bubbles

dots per inch

Unit of resolution in printing.

process

image: Wikimedia Commons, Galileo Galilei, Public domain

drawing

Image drawn by hand or by computer without relying on data.

figure, non-chart figures

drill-down

Moving from an aggregated level to a finer one.

interaction

dual axis

Two different vertical scales in the same chart.

critique

dual coding

Reinforcement of information through two distinct channels.

perception

dumbbell chart

Two joined dots showing the gap between two states.

chart, points and bubbles

ecological fallacy

Conclusion about individuals drawn from aggregated data.

critique

effect size

Measure of an effect's magnitude independent of sample size.

statistics

effectiveness principle

The most important attributes are encoded with the most salient channels.

encoding

efficiency

Quality of a construction answering a question correctly in a shorter observation time than another.

critique

eigenvalue

Amount of variance carried by an ordination axis.

statistics

elementary reading

Question bearing on a single element: at this date what is the value?

perception

empirical cumulative distribution function

Curve giving the share of observations below each value.

chart, lines and areas

enclosure

A shared frame creates a group.

perception

Equal Earth projection

Pseudocylindrical equal-area projection designed in 2018 after the look of the Robinson projection.

map

equal interval classification

Classification into classes spanning equal ranges of values.

map

equal-area projection

Projection preserving area ratios at the cost of shape.

map

error bar

Segment showing the spread or uncertainty of an estimate.

statistics

Euler diagram

Sets where only the actual intersections are drawn.

chart, sets

explanatory visualization

Visualization made to convey an identified message.

process

exploratory data analysis

Graphical examination of data without strong prior hypotheses.

process

exploratory visualization

Visualization made to discover structure for oneself.

process

expressiveness principle

Principle that “the visual encoding should express all of, and only, the information in the dataset attributes”.

encoding

external identification

Reading step where the observer recognizes what the graphic is about.

perception

extract (interaction)

Retrieval of a data subset together with its query parameters.

interaction

extrapolation

Projection of the data beyond the known points.

statistics

facet

Sub-chart obtained by splitting the data by a variable.

encoding

faceting

Splitting a chart into small multiples by a variable.

encoding

factor loading

Weight of a variable in the construction of an axis.

statistics

failure to account for statistical nuance

Conclusion ignoring a statistical subtlety such as the lack of a control group.

critique

fan chart

Forecast surrounded by widening uncertainty bands.

chart, lines and areas

figuration

Construction that must be read shape by shape because it does not fit into a single image.

perception

figure numbering

Figure referencing allowing them to be called out in the text.

process

figure title

Text announcing what a figure is about.

process

fill

Interior color of an area mark.

encoding

filtering (interaction)

Reducing the display to the selected observations.

interaction

flow chart

Diagram of the steps and decisions of a process.

chart, networks and trees

flow map

Map showing directed movement between places.

map, maps

focus indicator

Visual mark showing which element receives keyboard input.

interaction

font

A typeface in a given size and style.

typography

font weight

Stroke thickness of a typeface.

typography

forest plot

Effects and confidence intervals of several studies aligned.

chart, points and bubbles

frequency framing

Expressing a probability as a number of cases out of a total.

statistics

frequency polygon

Distribution drawn as a line joining the tops of the bins.

chart, lines and areas

funnel chart

Successive steps of a process with a shrinking population.

chart, bars

funnel plot

Effect against precision used to detect publication bias.

chart, points and bubbles

Gall-Peters projection

Cylindrical equal-area projection with standard parallels at 45 degrees.

map

Gantt chart

Horizontal bars placing tasks along a timeline.

chart, timelines

gauge chart

Circular dial showing a single value.

critique

geographic information system

System for managing and analyzing located data.

map

geometric symbol

Graphic symbol made of a point, a line, an area, a surface or a volume.

encoding

geometry

Type of mark used to represent the observations.

encoding

geospatial data

Data tied to a position on the Earth.

data

image: Wikimedia Commons, Mrmw, CC0

Gestalt principles

Rules describing how the eye groups visual elements.

perception

gist

Mental overview of a scene maintained despite eye movements.

perception

image: Wikimedia Commons, Wickey-nl, CC0

glyph

Small composite shape encoding several variables at once.

encoding

Goode homolosine projection

Interrupted equal-area projection joining the sinusoidal at low latitudes and the Mollweide at high latitudes.

map

grammar of graphics

Framework decomposing a chart into data, scales, geometries and layers.

encoding

grand tour

Animation of a continuous sequence of low-dimensional projections of multivariate data.

interaction

granularity

Size of the repeated elements of a texture at equal ink density.

encoding

image: Wikimedia Commons, Mikus, CC BY-SA 4.0

graph paper

Paper printed with a regular grid for plotting data by hand.

process

image: Wikimedia Commons, David Eppstein, CC0

graph theory

Branch of mathematics studying sets of vertices joined by edges.

statistics

graphic density

Number of signs relative to the available area.

critique

image: Wikimedia Commons, Burssens, CC BY-SA 4.0

graphic design

Design of the visual form of a message.

process

graphic processing

Reworking a graphic until it answers the question asked.

process

graphicacy

Ability to read and produce graphical representations.

perception

image: Wikimedia Commons, Meadow JF, Altrichter AE, Bateman AC, Stenson J, Brown G, Green JL, Bohannan BJM. 2015. Humans differ in their personal microbial cloud. PeerJ 3:e1258 https://doi.org/10.7717/peerj.1258, CC BY 4.0

graphical abstract

Single figure summarizing the point of an article.

process

graphical integrity

Faithfulness of the representation to the magnitude of the data it displays.

critique

graphical perception

Study of how accurately graphical encodings are read.

perception

graticule

Network of meridians and parallels drawn on a map.

map

gridline

Background line helping to read values.

encoding

grouped bar chart

Bars juxtaposed within groups to compare several series.

chart, bars

guided tour

Tour that steers the sequence of projections toward those showing a sought-after structure.

interaction

headline

Title stating the conclusion to draw from the chart rather than its topic.

process

heatmap

Matrix whose cells are colored by value.

chart, matrices and tables

hexbin map

Spatial aggregation into hexagonal cells.

map, maps

hexbin plot

Scatterplot whose plane is divided into hexagons shaded by the number of points.

chart, points and bubbles

hierarchical clustering

Grouping of observations into nested classes summarized by a dendrogram.

statistics

high-dimensional data

Data described by a large number of variables.

data

highlighting

Visual strengthening of a subset against the rest.

interaction

histogram

Distribution of a continuous variable split into bins.

chart, bars

history (interaction)

Log of user actions that supports undo and replay.

interaction

hive plot

Network whose nodes sit on radial axes according to their attributes.

chart, networks and trees

hockey stick chart

Long flat curve that bends sharply upward at the end of the series.

chart, lines and areas

horizon chart

Time series folded into colored bands to save vertical space.

chart, lines and areas

hyperbolic tree

Node-link tree drawn in hyperbolic geometry that enlarges the focus and squeezes the rest toward the edge of a disk.

chart, networks and trees

hypothetical outcome plot

Animation cycling through equally likely draws to show uncertainty.

statistics

icon

Small figurative image standing for a category or action.

encoding

iconic memory

Very brief visual memory, lasting a few hundred milliseconds, that holds an image just after it is seen.

perception

identity channel

Channel telling what something is or where it is suited to categorical attributes.

encoding

image

“Meaningful visual form perceived in an instant of perception (in a single glance)” (Bertin, translated).

perception

implantation

Geometric nature of the sign in Bertin: point, line or area.

encoding

imposition

Bertin's use of the plane: diagram, network, map or symbol.

encoding

incorrect reading of chart

Misreading induced by a flaw in the design of the chart.

critique

independent variable

Variable that is varied and does not depend on the other data in the chart.

data

index number

Series rescaled to 100 at a reference date.

data

induction

The reader's ability to draw far more from a graphic than the information deliberately put into it.

perception

image: Wikimedia Commons, Brian Solis and JESS3, CC BY 2.0

infographic

Graphic composition combining data, text and illustration.

process

information design

Design of artifacts that make information understandable.

process

information visualization

Visual representation of abstract non-spatial data.

process

inset

Small chart inserted inside a larger one.

encoding

insight need

Question a visualization must help answer.

process

interaction plot

Effect of one factor drawn separately for each level of another.

chart, lines and areas

interactivity

Ability for the reader to act on the representation.

interaction

internal identification

“Stage of the reading process during which the observer recognizes on the drawing the visual variables assigned to the components of the information” (Bertin, translated).

perception

interpolation

Estimating a value that falls between two known points.

statistics

interquartile range

Difference between the third and first quartiles, spanning the middle half of the values.

statistics

interval scale

Measurement with constant spacing but no absolute zero.

data

invariant

Notion common to all the data of a graphic and stated in the title.

encoding

inventory

Graphic representation recording the information exhaustively.

process

inverted axis

Axis running in reverse so that a rise reads as a fall.

critique

Ishikawa diagram

Fish-skeleton diagram that sorts the possible causes of an effect into categories, drawn as slanted bones along a central spine leading to the effect.

chart, networks and trees

ISOTYPE

Neurath's standardized pictogram system for statistics.

encoding

iteration

Successive rework of a figure from feedback.

process

jitter

Small random displacement of points to avoid overlap.

encoding

just-noticeable difference

Smallest detectable difference between two stimuli.

perception

image: Wikimedia Commons, Weston.pace, CC BY-SA 3.0

k-means

Partitioning into k classes that minimizes the distance of each observation to its class center.

statistics

kagi chart

Price chart without a time scale, drawn as a vertical line that turns back only when the price retraces by more than a preset amount.

chart, lines and areas

kerning

Adjustment of space between two adjacent characters.

typography

keyboard navigation

Browsing and operating a visualization with the keyboard alone.

interaction

image: Wikimedia Commons, Original: MarkSweep Vector: Andel, Public domain

kurtosis

Weight of a distribution's extreme values.

statistics

label

Text identifying an element of the chart.

encoding

Lambert conformal conic projection

Conformal conic projection, common for mid-latitude regions that extend east to west.

map

layer

Set of marks stacked on the previous ones in a chart.

encoding

layout grid

Invisible framework aligning the elements of a layout.

typography

leader line

Thin line joining a label to the element it names.

encoding

leading

Vertical space between successive baselines.

typography

learning objective

Statement of what the viewer should be able to do or feel after reading the visualization.

process

legend

Lookup table between graphical codes and categories.

encoding

legend toggle

Clickable legend hiding or revealing series.

interaction

legibility

Ability of a construction to let its signs be separated.

critique

length

Linear extent of a mark encoding a quantity.

encoding

length of a component

Number of distinct categories a component holds.

encoding

level of organization

Perceptual property of a visual variable: selective, ordered or quantitative.

encoding

level of reading

“Number of correspondences involved in an instant of perception” (Bertin, translated).

perception

lie factor

Ratio of the visual effect shown to the effect in the data.

critique

Likert chart

Ordered responses split either side of a neutral point.

chart, bars

line chart

Points joined by a line to show an ordered progression.

chart, lines and areas

line type

Line pattern such as solid, dashed or dotted.

encoding

linear discriminant analysis

Method that seeks the linear combinations of variables that best separate known groups.

statistics

linear regression

Fitting a line minimizing squared deviations.

statistics

linguistic symbol

Graphic symbol made of text, numerals or punctuation marks.

encoding

local tour

Tour that explores the projections close to a starting projection.

interaction

locator map

Simple map showing where the place discussed in the text lies.

map, maps

LOESS

Smoothing by successive local regressions.

statistics

logarithmic scale

Scale where a constant distance means a constant ratio.

encoding

lollipop chart

Thin stem topped by a dot replacing the bar.

chart, bars

long format

Table where measured variables are stacked into one column.

data

long-term memory

Durable store of knowledge that gives meaning to what is perceived.

perception

Lorenz curve

Curve giving, for each cumulative share of the population, the cumulative share of a quantity it holds, such as income.

chart, lines and areas

lossless compression

Image compression restoring the original pixel for pixel.

process

lossy compression

Image compression degrading the original to reduce file size.

process

magnitude channel

Channel perceived as ordered, suited to ordinal and quantitative attributes.

encoding

Manhattan plot

Significance of thousands of tests laid out along a genomic position.

chart, points and bubbles

image: Wikimedia Commons, L. Magado (Dessinateur des travaux hydrauliques du port de Brest), Public domain

map

Construction in which “the correspondences in the plane are established between the elements of a geographic component arranged in the observed geographic order” (Bertin, translated).

map, maps

map projection

Transformation of the globe onto a flat surface.

map

margin

Space reserved around the plotting area.

encoding

margin of error

Half-width of an estimate's confidence interval.

statistics

marginal plot

Small plot along the margin of a main plot showing the distribution of one of its variables.

encoding

Marimekko chart

Rectangles whose width and height encode two proportions.

chart, sectors, tilings and units

mark

Basic geometric element of a chart.

encoding

mean

Sum of values divided by their count.

statistics

measure

Width of a column of text.

typography

image: Wikimedia Commons, Blythwood, CC BY-SA 4.0

median

Value splitting the series into two equal halves.

statistics

memorability

Ease with which a figure stays in memory after being seen.

perception

Mercator projection

Conformal projection that greatly inflates high latitudes.

map

message

“Memorable graphic representation” (Bertin, translated).

process

metadata

Data describing the data itself.

data

misleading chart

Chart whose form leads to a false reading of the data.

critique

misrepresentation of scientific studies

Study invoked for a conclusion it does not support.

critique

missing data

Absent values that must be shown rather than hidden.

data

mockup

Faithful representation of the final rendering before build.

process

image: Wikimedia Commons, Joxemai, CC BY-SA 3.0

mode

Most frequent value.

statistics

model in the data space

Approach that shows a fitted model in the data space itself rather than through its summaries alone.

process

modifiable areal unit problem

Dependence of results on the chosen spatial partition.

critique

moiré effect

Spurious vibration produced by over-regular patterns.

critique

Mollweide projection

Elliptical equal-area projection common for thematic world maps.

map

monosemic graphic

Transcription of relationships between previously defined concepts.

encoding

monospaced typeface

Typeface where all characters share the same width.

typography

motion

Movement of a mark over time used as a visual variable.

encoding

motion parallax

Depth cue in which, as the viewer moves, near objects seem to move faster than far ones.

perception

moving average

Average computed over a sliding window.

statistics

multifunctioning graphical element

Element that fills several roles at once instead of just one.

encoding

natural breaks

Classification placing breaks so as to minimize variance within classes.

map

network

Construction in which “the correspondences in the plane can be established between all the elements of one and the same component” (Bertin, translated).

chart

network diagram

Nodes joined by links representing relationships.

chart, networks and trees

nominal scale

Measurement by plain unordered categories.

data

non-metric multidimensional scaling

Ordination preserving only the rank order of distances between objects.

statistics

nonlinear dimension reduction

Dimension reduction that can unfold a curved structure instead of projecting it.

statistics

image: Wikimedia Commons, Inductiveload, Public domain

normal distribution

Symmetric bell-shaped distribution.

statistics

normalization

Bringing values to a common base to make them comparable.

data

notched box plot

Box hollowed by a notch showing the uncertainty around the median.

chart, boxes and densities

ogive

Polygon joining the cumulative frequencies at the upper class limits.

chart, lines and areas

onion diagram

Set diagram of concentric circles in which each set lies strictly inside the one around it, from the most general to the most specific.

chart, sets

ordered variable

Visual variable whose categories order themselves spontaneously.

encoding

ordinal data

Categories with an order but no measurable spacing.

data

ordinal scale

Measurement by ordered categories without measurable spacing.

data

ordination

Projection of objects described by many variables into a low-dimensional space.

chart, points and bubbles

organizational chart

Tree of reporting lines within an organization.

chart, networks and trees

orientation

Tilt of a mark distinguishing categories.

encoding

original correspondence

“Meeting point of the elements of several components” (Bertin, translated).

encoding

orthographic projection

Projection showing the globe as seen from an infinitely distant point.

map

outlier

Observation far removed from the rest of the distribution.

statistics

overall reading

Question reducing the whole information to a single answer: what was the general trend?

perception

overplotting

Marks hiding one another in dense regions.

critique

overview first zoom and filter details on demand

Recommended design sequence for interactive exploration.

interaction

p-value

Probability of a result at least as extreme under the null hypothesis.

statistics

panel

Plotting area of a sub-chart.

encoding

panel label

Letter identifying one panel within a composite figure.

encoding

panning

Moving the viewport without changing scale.

interaction

pansemic graphic

The system opens onto any meaning.

encoding

parallel coordinates

Parallel axes crossed by one polyline per observation.

chart, lines and areas

parallel sets

Flows between the categories of several categorical variables.

chart, flows

parallelism

Placing comparable elements side by side so the comparison makes itself.

encoding

pattern

Motif whose repetition makes up a texture.

encoding

pattern recognition

Detection of regularities in an image.

perception

per capita

Related to the number of inhabitants.

data

percentage point

Unit of difference between two percentages.

data

percentile

Value below which a given percentage of observations fall.

statistics

perceptible step

Step of a visual variable that the eye can tell apart from its neighbor.

encoding

peripheral vision

Vision outside the center of gaze that detects motion and contrast, but little detail.

perception

perspective projection

Projection of a three-dimensional scene onto a plane in which distant objects appear smaller.

map

image: Wikimedia Commons, Louis Daguerre, Public domain

photograph

Image produced by a photographic process and reproduced as is.

figure, non-chart figures

phylogenetic tree

Tree showing the kinship relationships between taxa.

chart, networks and trees

pictogram

Repeated or stylized icon encoding a quantity or category.

chart, sectors, tilings and units

pictorial symbol

Graphic symbol made of an image, an icon or a statistical glyph.

encoding

pie chart

Disc split into sectors proportional to parts of a whole.

chart, sectors, tilings and units

piling

Concentration of points at the center of a low-dimensional projection of high-dimensional data.

critique

polar area chart

Equal-angle sectors whose radius encodes the value.

chart, radial

polar coordinates

Frame where position is given by an angle and a radius.

encoding

polysemic graphic

The system aims to define a concept or an idea but interpretations may diverge.

encoding

pop-out

Immediate standing out of a unique element in a set.

perception

population pyramid

Back-to-back bars comparing two groups by age class.

chart, bars

position

Location of a mark on a common scale.

encoding

position adjustment

Rule shifting overlapping marks to keep them readable.

encoding

position on unaligned scale

Location of a mark on a scale offset from those of the marks it is compared with.

encoding

preattentive processing

Immediate detection of some visual properties before focused attention.

perception

image: Wikimedia Commons, SV1XV, CC BY-SA 3.0

precision

Reproducibility of a measurement regardless of its correctness.

statistics

prediction interval

Interval expected to contain a future observation.

statistics

principal component analysis

Ordination seeking the axes that carry the most variance.

statistics

principle of proportional ink

The inked area representing a value must be proportional to that value.

critique

print output

Fixed medium imposing constrained resolution and color gamut.

process

progressive data analysis

Data analysis that delivers partial results of increasing quality while the computation runs.

process

projection (interaction)

Interactive change of the projection of multidimensional data onto the plane.

interaction

projection distortion

Alteration of angles, areas, distances or shapes that any projection of the globe onto a plane imposes.

map

projection pursuit

Search for low-dimensional projections that optimize an index of structure.

statistics

proportion

Fraction of a total.

data

proportional symbol map

Symbols sized by an absolute quantity at a location.

map, maps

proximity

Nearby elements are perceived as a group.

perception

psychophysics

Study of the link between physical and perceived magnitude.

perception

quantile classification

Classification putting the same number of observations in each class.

map

quantile dot plot

Probability distribution cut into a fixed number of quantiles each drawn as a dot.

chart, points and bubbles

quantile-quantile plot

Comparison of observed quantiles to a theoretical distribution.

chart, points and bubbles

quantitative data

Measured data on which arithmetic is meaningful.

data

quantitative variable

Visual variable allowing a numeric ratio to be read between two marks.

encoding

quartile

Value splitting the distribution into four equal parts.

statistics

radar chart

Axes radiating from a center joined into a polygon.

chart, radial

radial bar chart

Bars laid out along a circular axis.

chart, radial

radial tour

Tour that varies the share of a single variable in the projection to judge its importance.

interaction

raincloud plot

Combination of a density, a box and the raw points.

chart, boxes and densities

range bar chart

Bars that run, for each category, from a low value to a high value rather than from zero.

chart, bars

range of a quantitative series

“Ratio between the largest and the smallest number of the series” (Bertin, translated).

encoding

rarefaction curve

Expected richness as a function of sampling effort.

chart, lines and areas

raster graphics

Image described by a grid of pixels.

process

rate

Count related to a reference population.

data

ratio scale

Measurement with an absolute zero allowing ratios.

data

raw data

Data as collected before any processing.

data

reasoning error

Logical flaw in the conclusion drawn from a chart, even a faithfully plotted one.

critique

reference line

Line marking a notable value such as a threshold or a mean.

encoding

reflow

Rearranging enlarged content so it stays readable without scrolling in two directions.

interaction

image: Wikimedia Commons, Sewaqu, Public domain

regression

Model estimating one variable from one or more others.

statistics

relational analysis

Analysis of the links between entities.

statistics

reproducibility

Ability to rebuild the figure from the data and the code.

process

residual plot

Model residuals plotted against fitted values.

chart, points and bubbles

resolution

Pixel density of a raster image.

process

image: Wikimedia Commons, User:tfinc, CC BY-SA 3.0

responsive design

Adapting the layout to the screen size.

process

retina

Light-sensitive layer of the eye that converts light into nerve signals.

perception

retinal variable

Visual variable carried by the mark itself rather than by its location.

encoding

ribbon

Area delimiting the uncertainty around a line.

encoding

ridgeline plot

Vertically offset densities used to compare distributions.

chart, boxes and densities

Robinson projection

Compromise projection preserving neither angles nor areas but limiting both distortions.

map

ROC curve

Sensitivity against false positive rate of a classifier.

chart, lines and areas

rug plot

Short ticks along the margin of a chart marking the observed values.

encoding

sage tour

Tour that spreads projected points radially to correct their piling at the center.

interaction

saliency

Ability of an element to attract the eye.

perception

sample size

Number of observations an estimate rests on.

statistics

sampling

Selection of a representative subset of a population.

statistics

Sankey diagram

Flows whose width encodes a quantity conserved between stages.

chart, flows

sans serif

Letterforms without serifs.

typography

scagnostics

Numerical indices describing the shape of a scatterplot.

statistics

scale

Rule mapping data values to positions or colors.

encoding

scale bar

Segment of known length placed on the image to give its scale.

encoding

scale break

Break in the axis to absorb an extreme value.

critique

scatterplot

Points positioned by two quantitative variables.

chart, points and bubbles

scatterplot matrix

Grid of all pairwise scatterplots.

chart, points and bubbles

schematic

Simplified depiction of an object or process that encodes no data.

figure, non-chart figures

scientific visualization

Visual representation of data with a physical spatial support.

process

scree plot

Decreasing eigenvalues used to pick the number of axes.

chart, lines and areas

screen reader

Software rendering the content of a screen as speech or braille.

process

scrollytelling

Narrative whose steps trigger as the page scrolls.

interaction

search and locate (interaction)

Finding an item and highlighting its place in the view.

interaction

seizure risk

Hazard of a flash or red animation triggering an epileptic seizure.

critique

selectivity

Property of a visual variable that isolates a category at a glance.

perception

image: Wikimedia Commons, Original uploader was Denoir at en.wikipedia, CC BY-SA 2.5

self-organizing map

Neural network that places observations on a grid while preserving their neighborhoods.

statistics

semiology of graphics

Bertin's theory of how graphical signs work.

encoding

series

Sequence of related values within a table.

data

serif

Small terminal stroke on letterforms.

typography

shading

Continuous modulation of fill to suggest relief or intensity.

encoding

shape

Outline of a mark distinguishing categories.

encoding

image: Wikimedia Commons, M. W. Toews, CC BY-SA 4.0

shapefile

Geographic vector file format.

data

signal-to-noise ratio

Share of useful information against distracting elements.

critique

significance asterisks

Asterisks marking the significance threshold a comparison reaches.

encoding

similarity

Similar elements are perceived as a group.

perception

simplification

Cutting the number of elements until the question asked finds its answer.

process

Simpson's paradox

Reversal of a trend depending on whether groups are aggregated.

critique

image: Wikimedia Commons, Monarey, CC0

simultaneous contrast

Shift in perceived color caused by its surroundings.

perception

sina plot

Points of a distribution spread sideways in proportion to local density.

chart, points and bubbles

situational impairment

Temporary limitation caused by the context of use rather than by the person.

process

size

Dimension of a mark encoding a quantity.

encoding

sketch

Quick sketch exploring representation options.

process

image: Wikimedia Commons, Rodolfo Hermans (Godot) at en.wikipedia., CC BY-SA 3.0

skewed distribution

Distribution with one tail stretching much further than the other.

statistics

image: Wikimedia Commons, Rodolfo Hermans (Godot) at en.wikipedia., CC BY-SA 3.0

skewness

Imbalance of a distribution around its center.

statistics

slice tour

Tour that shows only the points near the projection plane to reveal the inside of shapes.

interaction

slopegraph

Two axes joined by segments showing change between two points.

chart, lines and areas

small caps

Capitals at lowercase height.

typography

small multiples

Series of identical charts repeated across categories.

chart, composites

smoothing

Damping of short-term variation to reveal the trend.

statistics

sonification

Rendering of data as sound rather than as images.

encoding

sorting

Ordering categories by value rather than alphabetically.

encoding

spaghetti chart

Unreadable overlay of too many lines.

critique

sparkline

Small axis-free chart embedded in running text.

chart, lines and areas

spatial region

Bounded area of the plane grouping the marks of one category.

encoding

spatial variable

Visual variable that places a mark along x, y or z.

encoding

spin-and-brush

Manual clustering that colors the groups spotted while projections rotate.

interaction

spine chart

Single value split into two opposed components either side of an axis.

chart, bars

stacked area chart

Areas cumulated on top of one another.

chart, lines and areas

stacked bar chart

Bars split into segments that sum to the total.

chart, bars

image: Wikimedia Commons, M. W. Toews, CC BY 2.5

standard deviation

Measure of spread around the mean.

statistics

standard error

Standard deviation of the sampling distribution of an estimate.

statistics

static visualization

Fixed representation that the reader cannot manipulate.

process

statistical graphics

The field concerned with the visual display of quantitative data.

process

statistical significance

Difference judged unlikely under chance alone.

statistics

statistical transformation

Computation applied to the data before drawing, such as a count or a smooth.

encoding

stem-and-leaf plot

Distribution where each value stays readable, the leading digit forming the stem and the next the leaf.

chart, text

step chart

Line with plateaus marking discrete changes.

chart, lines and areas

stereographic projection

Conformal azimuthal projection that projects the globe from the point opposite the point of tangency.

map

Stevens' power law

Perceived magnitude follows a power function of physical magnitude.

perception

storyboard

Sequence of sketches setting the order and content of the steps of a story.

process

streamgraph

Stacked areas around a floating central baseline.

chart, lines and areas

streamline plot

Curves tangent at every point to the direction of a vector field, such as a wind or a current.

chart, flows

stress

Measure of the disagreement between projected and observed distances.

statistics

strip plot

Individual values projected onto a single axis.

chart, points and bubbles

stroke

Line delimiting a mark.

encoding

style guide

Document fixing colors, typefaces and graphical conventions.

process

sunburst

Hierarchy shown as subdivided concentric rings.

chart, sectors, tilings and units

supplementary figure

Figure published as an appendix rather than in the body of the article.

process

surplus-deficit filled line

Line whose area is filled either side of a baseline to contrast surplus and deficit.

chart, lines and areas

survival curve

Share of subjects still event-free over time.

chart, lines and areas

SVG

Vector format of the web where each mark stays an addressable object.

process

symbolization

Choice of the symbols and visual variables that stand for each datum on a map.

map

t-SNE

Nonlinear dimensionality reduction preserving local neighborhoods.

statistics

table sorting

Ordering rows by a meaningful column.

encoding

tabular figures

Digits of equal width intended for columns of numbers.

typography

tape diagram

Row of rectangles whose lengths stand for the quantities of an arithmetic word problem and their relations, used to find the unknown.

figure, non-chart figures

task typology

Classification of the tasks a reader or analyst performs with a visualization.

process

template

Reusable graphical structure for a series of figures.

process

ternary plot

Scatterplot drawn in a triangle, where each point's position gives the shares of three components of a single whole.

chart, points and bubbles

text excerpt

Passage of text reproduced as a figure for its content or layout.

figure, non-chart figures

texture

Visual variable formed by the repeated elements filling a mark.

encoding

thematic map

Map devoted to showing a phenomenon rather than to locating.

map, maps

theme

All graphical settings independent of the data.

encoding

tick label

Value written next to a tick mark.

encoding

tick mark

Marker indicating a value on an axis.

encoding

tidy data

Format where each variable is a column and each observation a row.

data

tile map

Schematic map where each unit occupies an equal-size cell.

map, maps

time series

Sequence of values indexed by time.

data

time-series decomposition

Splitting a time series into trend, seasonality and remainder.

statistics

timeline

Events laid out along a time axis.

chart, timelines

tooltip

Panel shown on hover giving the detail of an element.

interaction

topographic map

Map depicting the relief and ground features of an area.

map

tornado chart

Opposed bars ranked by magnitude for a sensitivity analysis.

chart, bars

tour path

Ordered sequence of projections traversed by a tour.

interaction

tracking

Overall setting of space between characters.

typography

transition

Animated change preserving continuity between two states.

interaction

transverse Mercator projection

Mercator projection whose cylinder touches the globe along a meridian, conformal and little distorted near that meridian.

map

treemap

Hierarchy tiled with nested rectangles sized by value.

chart, sectors, tilings and units

trend line

Curve summarizing the general direction of a scatter.

statistics

trueness

Closeness of the mean of a large number of measurements to the true value.

statistics

truncated axis

Axis not starting at zero which exaggerates differences.

critique

tube map

Topological schematic with strokes limited to a few angles.

chart, networks and trees

image: Wikimedia Commons, William Caslon, Public domain

typeface

Coherent set of letterform designs.

typography

image: Wikimedia Commons, Willi Heidelbach, CC BY 2.5

typography

Art of arranging type to make text legible and meaningful.

typography

UMAP

Nonlinear dimensionality reduction based on the neighborhood structure of the data.

statistics

uncertainty

Range of values compatible with the observed data.

statistics

unimodal distribution

Distribution with a single peak, or mode.

statistics

unit chart

One elementary shape per counted unit.

chart, sectors, tilings and units

univariate analysis

Study of one variable at a time: its distribution, central tendency and spread.

statistics

UpSet plot

Set intersections shown as bars rather than overlapping circles.

chart, sets

value

Position of a fill between light and dark.

encoding

image: Wikimedia Commons, JRBrown, Public domain

variance

Square of the standard deviation measuring spread.

statistics

vector graphics

Image described by geometric shapes rather than pixels.

process

Venn diagram

Overlapping circles showing set intersections.

chart, sets

viewer

Person who receives the visualization and reads it.

process

violin plot

Distribution density mirrored on both sides of an axis.

chart, boxes and densities

virtual reality

Simulated three-dimensional environment in which the user is immersed.

interaction

visual cortex

Brain region that processes the signals coming from the retina.

perception

visual cue

Graphical property the reader uses to interpret.

perception

visual encoding

Mapping of data onto graphical properties.

encoding

visual hierarchy

Reading order created by contrasts of size and weight.

typography

visual idiom

Particular combination of encoding and interaction forming a view type.

encoding

visual variable

Graphical property carrying information in Bertin's sense.

encoding

visual vocabulary

Catalog of chart types arranged by reading intent.

process

visual working memory

Limited capacity for temporarily holding visual elements.

perception

volcano plot

Effect size against significance in high-throughput analysis.

chart, points and bubbles

volume

Apparent volume of a mark encoding a quantity.

critique

Voronoi diagram

Tiling of the plane into nearest-neighbor cells.

chart, sectors, tilings and units

waffle chart

Grid of squares whose count encodes a proportion.

chart, sectors, tilings and units

waterfall chart

Breakdown of a change into positive and negative contributions.

chart, bars

Waterman butterfly projection

Polyhedral projection unfolding the globe into a butterfly shape from a truncated octahedron.

map

web scraping

Automated retrieval of data published on the web.

process

Weber's law

The discrimination threshold grows in proportion to intensity.

perception

wheat plot

Dot plot binned like a histogram in which each dot stays at its exact value.

chart, points and bubbles

whisker

Segment extending the box out to the retained extreme values.

encoding

white space

Empty areas that structure the layout.

typography

wide format

Table where each measure has its own column.

data

wind map

Map showing wind direction and strength through oriented or animated strokes.

map, maps

wind rose

Polar diagram of frequencies by direction.

chart, radial

wireframe

Structural sketch without final graphic content.

process

word cloud

Words whose size encodes frequency.

chart, text

word tree

Branching of word sequences following a pivot term.

chart, networks and trees

x-axis

Horizontal axis of the coordinate system.

encoding

x-height

Height of lowercase letters without ascenders.

typography

y-axis

Vertical axis of the coordinate system.

encoding

zooming (interaction)

Changing the display scale over a region.

interaction