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Multivariate Data – More Overview

Multivariate Data – More Overview. CS 4460 - Information Visualization Jim Foley Original PPts John Stasko , augmented by J. Foley. Some Key Concepts. Data Types Data Marks. Data Types. Four types of data variables N-Nominal Equal or not equal to other values Example: gender

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Multivariate Data – More Overview

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  1. Multivariate Data – More Overview CS 4460 - Information Visualization Jim Foley Original PPts John Stasko, augmented by J. Foley.

  2. Some Key Concepts • Data Types • Data Marks

  3. Data Types • Four types of data variables • N-Nominal • Equal or not equal to other values • Example: gender • O-Ordinal • Obeys < relation, ordered set • Example: fr, so, jr, sr • I-Interval • Can do math, arbitrary zero; intervals are equal; ratios not meaningful • Examples: Year in Julian calendar; degrees Farenheit • R-Ratio • Can do math; ratios are meaningful • Examples: Degrees Kelvin; your age

  4. What are These Variable Types? • Nominal, Ordinal, Interval, Ratio? • Cars • make • model • year • miles per gallon • cost • number of cylinders • weight CS 4460

  5. Data Marks • Data Marks are visual primitives in 2D or 3D space • Points • Lines • Areas • Volumes • Graphical Propertiesof Data Marks encode variables • Size, shape • Color (HSV) • Orientation • Texture • Border • Information Presentations are built up of Data Marks

  6. How Select Best Variable Encodings? Match Data Type with appropriate Data Mark / Graphical Properties Does it make sense to encode gender with size of a circle? Does it make sense to encode salaries for various occupations with shape of a mark (square, triangle, circle, diamond, etc?)

  7. Estimated Accuracy of Information Codings MacKinlay (ACM TOGS 5, 2, April 1986).Based partially on experiments by Cleveland and McGill.

  8. Pie Charts: Usually Bivariate (N=2) What does 3D add? Note double key – color and legend CS 4460

  9. Pie Charts Bivariate or Trivariate? • What data types are most commonly depicted with pie charts? • Identification of each slice – what data type? • Size of each slice – what data type? • How many variables could one encode in a pie chart? For each slice • Size • Color (H, S, V) • Height • Texture • Would the chartbe useful? CS 4460

  10. Hypervariate Data N > 3 • Number of well-known visualization techniques exist for data sets of 1-3 dimensions • line graphs, bar graphs, scatter plots OK • We see a 3-D world (4-D with time) • What about data sets with more than 3 variables? • Often the interesting, challenging ones • Could use additional data mark properties to encode additional data variables. CS 4460

  11. Bar Chart Show the relationships between variables’values in a data table What are their types? How many variables? CS 4460

  12. Bar Chart Show the relationships between variables’values in a data table What are their types? Region – Nominal Sales – Ratio Quarter – Ordinal How many variables? Region Quarter Sales CS 4460

  13. Gallery of Bar Charts CS 4460 How many variables and cases?

  14. Small Multiples: Star Plot N>3 N = 10; Car type + 9 data items per car type N = 4 (5 if include case index/number); created at http://www.wessa.net/rwasp_starplot.wasp CS 4460

  15. Chernoff Faces N>3 Encode different variables’ values in characteristics of human face N=11 in this example Cute Not so useful  Cute applets: http://www.cs.uchicago.edu/~wiseman/chernoff/ http://hesketh.com/schampeo/projects/Faces/chernoff.html CS 4460

  16. Small Multiples: Chernoff Faces N>3 Useful?? CS 4460

  17. How Many Variables? BTW this is called a “stacked bar chart” Critique?? Several issues!! From http://peltiertech.com/WordPress/trellis-plot-alternative-to-stacked-bar-chart/ CS 4460

  18. “Magic Quadrant” How many variables? • How many columns in table? • Any ancillary information CS 4460

  19. InfoScope Free download from http://www.macrofocus.com/public/products/infoscope/download/ Live Demo CS 4460

  20. Takeaways – what are they? … … 3… 4… CS 4460

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