Visual Encodings (Continued), Color CS 7250 S PRING 2020 Prof. - PowerPoint PPT Presentation

Visual Encodings (Continued), Color CS 7250 S PRING 2020 Prof. Cody Dunne N ORTHEASTERN U NIVERSITY Slides and inspiration from Michelle Borkin, Krzysztof Gajos, Hanspeter Pfister, 1 Miriah Meyer, Jonathan Schwabish, and David Sprague

R EADING Q UIZ 5 min 2

B URNING Q UESTIONS ? 3

P REVIOUSLY , ON CS 7250… 4

Analysis What data is shown? Why is the user analyzing / viewing it? How is the data presented? 5

Analysis D ATA A BSTRACTION T ASK A BSTRACTION V ISUAL E NCODING 6

V ISUAL E NCODING 7

Arrange Tables Categorical or Ordinal Key: an independent attribute that can be used as a unique index (Tableau Dimension) Value: a dependent attribute (i.e., cell in a Categorical Ordinal, or table) (Tableau Measures) Quantitative 8

N OW , ON CS 7250… 9

Analysis D ATA A BSTRACTION T ASK A BSTRACTION V ISUAL E NCODING 10

G OALS FOR T ODAY • Learn (still more) about visual encodings, esp. arranging tables • Learn how to pick appropriate visual representations based on attribute type and perceptual properties 11

How to handle multiple keys...? Gratzel et al., 2013 12

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Divergent The Economist, 2012 14

Time Series (Quantitative data over time) 15

Time Series (Quantitative data over time) Cody Dunne, Nightscout Foundation, 2020 16

Time Series Distributions (Quantitative data over time) Cody Dunne, Nightscout Foundation, 2020 17

Distributions & Correlations 18

Distributions & Correlations Lower Quartile Upper Quartile Outlier Median Minimum Maximum B OX AND W HISKER P LOT 19

Dichotomous statistical thinking is problematic (e.g., p <.05 = significant)… and this means nothing w/o context about the tests used!!! Xkcd, 2009 Besançon & Dragicevic, 2019 20

Distributions & Correlations Brehmer, 2016 21

Distributions & Correlations 22

Distributions & Correlations Interactive online: Sielen, 2018 23

Matejka &Fitzmaurice, 2017

Distributions & Correlations T REND /C ORRELATION L INE 25

Distributions & Correlations 26

Matejka &Fitzmaurice, 2017

SpaceTree (Plaisant et al., 2002) YouTube TreeJuxtaposer (Munzner et al., 2003) YouTube 28

http://massvis.mit.edu/ Borkin, M., Vo, A., Bylinskii, Z., Isola, P., Sunkavalli, S., Oliva, A., & Pfister, H., 2013, "What Makes a Visualization Memorable?", IEEE Transactions on Visualization and Computer Graphics (Proceedings of InfoVis 2013), 19, 12, 2306-2315. Great resource for categorizing visualizations, and brainstorming! 29

More visualization “catalogs” DataVizProject The Data Visualization Catalogue http://datavizproject.com/ http://www.datavizcatalogue.com/ 30

More visualization ideas https://matplotlib.org/gallery.html https://github.com/d3/d3/wiki/Gallery https://plot.ly/python/ 31

C OLOR 32

G OALS FOR T ODAY : LEARN H OW … • …to effectively use color as a channel for visual encodings including different colormap types. • …we process color in the visual system. • …individual color differences (i.e., colorblindness) should be accommodated in visualizations. • …interactions can occur between colors and with lighting. • …illusions and tricks can affect perception. 33

Color Maps Color Map = map between value (domain) and color (range) 34 matplotlib Bostock, 2018

“…avoiding catastrophe becomes the first principle in bringing color to information: above all, do no harm.” -Edward Tufte Tufte, “Envisioning Information” 35

Color Vocabulary and Perceptual Ordering Darkness (Lightness) Saturation Hue ? ? Based on Slides by Miriah Meyer, Tamara Munzner 36

≈Darkness (Lightness) VAD Chapter 10 37

Color Maps T HREE M AIN T YPES : Categorical Does not imply magnitude differences (categorical/nominal data) Distinct hues with similar emphasis Sequential Best for ordered data that progresses from low to high (ordinal, quantitative data) Darkness (lightness) channel effectively employed For data with a “diverging” (mid) point Diverging (quantitative data) Equal emphasis on mid-range critical values and extremes at both ends of the data range 38 Brewer, 1994

Color Maps A LSO ... Bivariate Displays two variables Combination of two sequential color schemes These are very difficult to design effectively, make intelligible, and be color blind friendly. + = 39 Stevens, 2015

Sequential (single hue) Types of Color Maps Diverging Sequential (multiple hue) Categorical Cyclical 40 Bostock, 2018

R ODS & C ONES Red Green Blue trichromacy = possessing three independent channels for conveying color information Ask a Biologist 41

R ODS & C ONES http://i.stack.imgur.com/wIbcE.jpg 42 Dubuc, 2002

C ONES & R ODS This is why darkness (lightness) is an effective encoding channel! Rods:120 million Cones: 5-6 million This is why we are so Cones: sensitive to red! 64% red-sensitive 32% green-sensitive 2% blue-sensitive. Witcombe, 2014 43

Darkness (Lightness) Channel • No edges without darkness difference • No shading without darkness variation • Has higher spatial sensitivity than color channels • Contrast defines legibility, attention, layering • Controlling darkness is primary rule of design Based on Slide by Hanpseter Pfister 44

“Get it right in black and white.” -Maureen Stone Stone, 2010 45

Stone, 2010 46

Understanding your medium matters

FatFonts Nacenta et al., 2012 48