Data Visualization Quiz 3

Eliminate Clutter

Include only what adds to the audience's understanding, remove everything else

aes()

aesthetic mapping, map data to elements of the chart

ggplot

create any chart, need to add various elements on at a time for display

qplot

create basic charts, can send aesthetic mappings in as parameters

data-ink ratio

data-ink/total ink used to print graphic

avoid diagonal components including lines and text

e.g. people read text rotated at 45 degrees ~50% slower than normal text

Gestalt Principle: connection

elements tend to be grouped together if they are connected by another element

Gestalt Principle: similarity

elements tend to be integrated into groups if they are similar to each other

Gestalt Principle: enclosure

elements tend to be integrated into groups if they are within an enclosure

Gestalt Principle: closure/continuity

elements tend to be integrated into groups if they are within an enclosure. your brain fills in the rest of the shape even though parts are removed

Gestalt Principle: proximity

elements tend to be perceived as aggregated into groups if they are near each other. strongest principles

Clutter

elements that take up space/use ink but do not increase understanding

we "see" with a combination of our

eye(s)

often default behavior in data visualization tools create...

more contrasting elements than are needed

without visual cues...

most readers will read in a z-shaped pattern from left to right, then down a line, and so on.

whitespace means

no non-data-ink

Data-ink

non-erasable ink used for the presentation of data (i.e. if any of the data-ink is removed, the graphic would lose content)

intensity (saturation)

ordered data with a few values, ordinal data, broadly supported, will generally require a legend to define the order, be careful of visual habits e.g. temperature ranges often represented by a red to blue scale

line width

ordered data with a few values, ordinal data, supported by some data viz tools (your instructor thinks this one is silly)

orientation

ordered data with a few values, quantitative data, ordinal data, not commonly supported

Size

ordered data with many useful values, quantitative data, ordinal data, broadly supported data viz tools, sometimes size is used when shape is a better encoding

line length

ordered data with many values, quantitative data, ordinal data, this preattentive attribute explains why bar charts are very effective for their use, broadly supported in data viz tools

position

ordered data with many values, quantitative value, ordinal data, categorical data, relationship data, broadly supported, note: listed twice once as a way to reduce cognitive load and again as a way to draw attention

Create clean horizontal and vertical lines in the design

otherwise readers will read left to right, then down and so on

ggplot2

package created by Hadley Wickam to increase the functionality of plotting in R

Gestalten

plural form of Gestalt

applicable gestalts with whitespace

proximity, enclosure

5 gestalt principles

proximity, similarity, enclosure, closure/continuity, connection

the data-ink ratio represents...

the proportion of the graphics ink devoted to the non-redundant display of data/information

consider the following and use whitespace liberally:

tufte's data-ink ratio

directing the audience

"enhancing the understanding" by providing direction

removing clutter

"not hurting" your audience

Chartjunk

"useless, non-informative, or information-obscuring elements of quantitative information displays"

light comes into...

the lens and focuses on the retina

Edward Tufte quote #2

Above all else, show the data

Chartjunk quote credit

Edward Tufte

theme

allows the user to control the overall look and feel

ggplot is flexible...

and extensible way to generate graphics

the eye-brain system has...

approx 1000x the resolution of a standard power point slide

Throughput is approx. 10 Mbps(each)

brain

retina is made from

brain cells (seeing and thinking are one at this point)

"Editor"

chooses, forgets, summarizes, focus, etc.

facets

generates the same plot for different slices of the data. will cover in lab 4

examples of geom

geom_point (scatterplot), geom_bar (bar chart), geom_line (line chart), geom_hline (add a horizontal line)

geom

geometrical objects added to layers of the chart.

Every element added....

increases cognitive load

2 main functions to generate plots

qplot, ggplot

gestalt principles

rules of the organization of perceptual scenes.they aim to formulate the regularities according to which the perceptual input is organized into unitary forms, also referred to as (sub)wholes, groups, groupings, or Gestalten (the plural form of Gestalt)

guideline: use preattentive attributes

sparingly; too many reduces focus for the audience

process steps:

start with everything "untreated", "treat" aspects of the data viz one at a time with an effective preattentive attribute, stop before you add to many "treatments"

contrasts directs...

the audience

scales

this set of functions allows the user to control the axes

3-8 seconds

time to get reader's attention

ggplot2 allows the user

to programmatically control nearly every element of the chart

hue (color)

unordered data with a few values (5 is getting to be too many), categorical data, broadly supported, don't over-do it many data viz tools wil run out of different colors and then wrap the colors so two different elements can be represented by the same color (confusing!), be aware that a portion of your audience may be color blind and won't be able to distinguish between certain color combinations.

shape

unordered data with a medium number of values, categorical data, broadly supported, make sure shapes are mapped to the same data across different visuals (otherwise, confusion follows)

added marks

unordered data with a medium number of values, categorical data, mostly represented by call-outs in charts

enclosure

unordered data with many values, categorical data, relationship data, most often represented by call-out boxes overlaying some portion of the chart

results from this step travel...

via the optic nerve to the brain. Optic nerves

Gestalt

your brain filling in the gaps