Data Visualization: Multivariate Data Sets and Representations in CS 7450 - Prof. John Sta, Assignments of Computer Science

Download Data Visualization: Multivariate Data Sets and Representations in CS 7450 - Prof. John Sta and more Assignments Computer Science in PDF only on Docsity! 1 Multivariate Data Sets & Representations CS 7450 - Information Visualization Jan. 21, 2003 John Stasko Spring 2003 CS 7450 2 Agenda • Data forms and representations • Basic representation techniques • Multivariate (>3) techniques Spring 2003 CS 7450 3 Data Sets • Data comes in many different forms • Typically, not in the way you want it • How is stored (in the raw)? 2 Spring 2003 CS 7450 4 Example • Cars − make − model − year − miles per gallon − cost − number of cylinders − weights − ... Spring 2003 CS 7450 5 Example • Web pages Spring 2003 CS 7450 6 Data Tables • Often, we take raw data and transform it into a form that is more workable • Main idea: − Individual items are called cases − Cases have variables (attributes) 5 Spring 2003 CS 7450 13 Representation • What’s a common way of visually representing multivariate data sets? • Graphs! Spring 2003 CS 7450 14 Basic Symbolic Displays • Graphs ß • Charts • Maps • Diagrams From: S. Kosslyn , “Understanding charts and graphs”, Applied Cognitive Psychology, 1989. Spring 2003 CS 7450 15 1. Graph Showing the relationships between variables’ values in a data table 0 20 40 60 80 100 1st Qtr 2nd Qtr 3rd Qtr 4th Qtr East West North 6 Spring 2003 CS 7450 16 Properties • Graph − Visual display that illustrates one or more relationships among entities − Shorthand way to present information − Allows a trend, pattern or comparison to be easily comprehended Spring 2003 CS 7450 17 Issues • Critical to remain task-centric − Why do you need a graph? − What questions are being answered? − What data is needed to answer those questions? − Who is the audience? time money Spring 2003 CS 7450 18 Graph Components • Framework − Measurement types, scale • Content − Marks, lines, points • Labels − Title, axes, ticks 7 Spring 2003 CS 7450 19 Other Symbolic Displays • Chart • Map • Diagram Spring 2003 CS 7450 20 2. Chart • Structure is important, relates entities to each other • Primarily uses lines, enclosure, position to link entities Examples: flowchart, family tree, org chart, ... Spring 2003 CS 7450 21 3. Map • Representation of spatial relations • Locations identified by labels 10 Spring 2003 CS 7450 28 Marks • Things that occur in space − Points − Lines − Areas − Volumes Spring 2003 CS 7450 29 Graphical Properties • Size, shape, color, orientation... Spatial properties Object properties Expressing extent Differentiating marks Position Size Grayscale Orientation Color Shape Texture Spring 2003 CS 7450 30 Back to Data • What were the different types of data sets? • Number of variables per class − 1 - Univariate data − 2 - Bivariate data − 3 - Trivariate data − >3 - Hypervariate data 11 Spring 2003 CS 7450 31 Univariate Data • Representations 7 5 3 1 Bill 0 20 Mean low highMiddle 50% Tukey box plot Spring 2003 CS 7450 32 What goes where • In univariate representations, we often think of the data case as being shown along one dimension, and the value in another Line graph Bar graph Y-axis is quantitative variable See changes over consecutive values Y-axis is quantitative variable Compare relative point values Spring 2003 CS 7450 33 Alternative View • We may think of graph as representing independent (data case) and dependent (value) variables • Guideline: − Independent vs. dependent variables Put independent on x-axis See resultant dependent variables along y -axis 12 Spring 2003 CS 7450 34 Bivariate Data • Representations Scatter plot is common price mileage Two variables, want to see relationship Is there a linear, curved or random pattern? Each mark is now a data case Spring 2003 CS 7450 35 Trivariate Data • Representations 3D scatter plot is possible horsepower mileage price Spring 2003 CS 7450 36 Alternative Representation Still use 2D but have mark property represent third variable 15 Spring 2003 CS 7450 43 Star Plot examples http://seamonkey.ed.asu.edu/~ behrens /asu /reports/compre/comp1.html Spring 2003 CS 7450 44 Star Coordinates E. Kandogan, “Star Coordinates: A Multi-dimensional Visualization Technique with Uniform Treatment of Dimensions”, InfoVis 2000 Late-Breaking Hot Topics, Oct. 2000 Demo Spring 2003 CS 7450 45 Parallel Coordinates • What are they? − Explain… 16 Spring 2003 CS 7450 46 Parallel Coordinates V1 V2 V3 V4 V5 Encode variables along a horizontal row Vertical line specifies values Spring 2003 CS 7450 47 Parallel Coords Example Basic Grayscale Color Spring 2003 CS 7450 48 Application • System that uses parallel coordinates for information analysis and discovery • Interactive tool − Can focus on certain data items − Color Taken from: A. Inselberg, “Multidimensional Detective” InfoVis ‘97, 1997. 17 Spring 2003 CS 7450 49 Discuss • What was their domain? • What was their problem? • What were their data sets? Spring 2003 CS 7450 50 The Problem • VLSI chip manufacture • Want high quality chips (high speed) and a high yield batch (% of useful chips) • Able to track defects • Hypothesis: No defects gives desired chip types • 473 batches of data Spring 2003 CS 7450 51 The Data • 16 variables − X1 - yield − X2 - quality − X3-X12 - # defects (inverted) − X13-X16 - physical parameters