Encode tables: Arrange space How? How? Encode Manipulate Facet Encode Manipulate Facet Encode Encode Manipulate Facet Reduce Encode Map Arrange Change Juxtapose Filter Arrange Week 2: from categorical and ordered Express Separate Express Separate Arrange attributes Color Express Separate Chart Types and Best Practices Hue Saturation Luminance Select Partition Aggregate Order Align Order Align Size, Angle, Curvature, ... Use Tamara Munzner Navigate Superimpose Embed Order Align Shape Department of Computer Science University of British Columbia Motion Direction, Rate, Frequency, ... JRNL 520H, Special Topics in Contemporary Journalism: Data Visualization Week 2: 19 September 2017 www.cs.ubc.ca/~tmm/courses/journ17 2 3 4 Idiom: scatterplot Idiom: bar chart Keys and values Some keys: Categorical regions Tables 100 100 Express Values • key • express values • one key, one value 75 75 Attributes (columns) Separate Order Align 50 50 –independent attribute Items –quantitative attributes –data (rows) 25 25 –used as unique index to look up items • 1 categ attrib, 1 quant attrib • no keys, only values 0 0 Cell containing value –mark: lines –simple tables: 1 key –data –channels –multidimensional tables: multiple keys Multidimensional Table • 2 quant attribs Animal Type Animal Type • length to express quant value • regions : contiguous bounded areas distinct from each other • value –mark: points • spatial regions: one per mark –channels –using space to separate (proximity) –dependent attribute, value of cell – separated horizontally, aligned vertically Value in cell • horiz + vert position –following expressiveness principle for categorical attributes • classify arrangements by key count – ordered by quant attrib –tasks • use ordered attribute to order and align regions » by label (alphabetical), by length attrib (data-driven) –0, 1, 2, many... • find trends, outliers, distribution, correlation, clusters –task 1 Key 2 Keys 3 Keys Many Keys Express Values –scalability 1 Key 2 Keys 3 Keys Many Keys • compare, lookup values List Matrix Volume Recursive Subdivision List Matrix Volume Recursive Subdivision –scalability • hundreds of items • dozens to hundreds of levels for key attrib [A layered grammar of graphics. Wickham. Journ. Computational and Graphical Statistics 19:1 (2010), 3–28.] 5 6 7 8 Idiom: stacked bar chart Separated and Aligned but not Ordered Separated, Aligned and Ordered Separated but not Ordered or Aligned • one more key –data • 2 categ attrib, 1 quant attrib –mark: vertical stack of line marks • glyph : composite object, internal structure from multiple marks –channels [Using Visualization to Understand the • length and color hue Behavior of Computer Systems. Bosch. Ph.D. • spatial regions: one per glyph thesis, Stanford Computer Science, 2001.] – aligned: full glyph, lowest bar component – unaligned: other bar components –task • part-to-whole relationship –scalability LIMITATION: Hard to know rank. What’s the 4 th most? The 7 th ? LIMITATION: Hard to make comparisons • several to one dozen levels for stacked attrib [Slide courtesy of Ben Jones] [Slide courtesy of Ben Jones] [Slide courtesy of Ben Jones] 12 Idiom: streamgraph Idiom: line chart Choosing bar vs line charts Idiom: heatmap 60 60 20 50 50 • generalized stacked graph • one key, one value • depends on type of key • two keys, one value 40 40 15 30 30 attrib –emphasizing horizontal continuity –data –data 20 20 10 10 10 –bar charts if categorical • vs vertical items • 2 quant attribs • 2 categ attribs (gene, experimental condition) 0 0 Female Male 5 Female Male [Stacked Graphs Geometry & Aesthetics. Byron and Wattenberg. • 1 quant attrib (expression levels) –data –mark: points –line charts if ordered IEEE Trans. Visualization and Computer Graphics (Proc. InfoVis 0 60 60 2008) 14(6): 1245–1252, (2008).] –marks: area • 1 categ key attrib (artist) • line connection marks between them 50 50 • do not use line charts for 40 40 • 1 ordered key attrib (time) –channels • separate and align in 2D matrix categorical key attribs 30 30 20 20 Year – indexed by 2 categorical attributes • 1 quant value attrib (counts) • aligned lengths to express quant value Many Keys 10 10 1 Key 2 Keys –violates expressiveness –channels –derived data 0 0 • separated and ordered by key attrib into horizontal regions 10-year-olds 12-year-olds List Matrix Recursive Subdivision 10-year-olds 12-year-olds principle • color by quant attrib • geometry: layers, where height encodes counts –task after [Bars and Lines: A Study of Graphic Communication. Zacks and Tversky. • implication of trend so strong Memory and Cognition 27:6 (1999), 1073–1079.] – (ordered diverging colormap) • 1 quant attrib (layer ordering) • find trend that it overrides semantics! –task –scalability – connection marks emphasize ordering of items along key axis by explicitly showing relationship – “The more male a person is, the between one item and the next • find clusters, outliers taller he/she is” • hundreds of time keys –scalability • dozens to hundreds of artist keys • 1M items, 100s of categ levels, ~10 quant attrib levels – more than stacked bars, since most layers don’t extend across whole chart 13 14 15 16
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