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  1. 1. Graphing Your Data: Graphing Software and Other Tips Priti Shah
  2. 2. Goals <ul><li>Communicating an important quantitative fact (e.g. an interaction) to an audience (talk, journal article) </li></ul><ul><li>Exploratory Data analysis (trying to figure out what your data say </li></ul>
  3. 3. Software options <ul><li>Macintosh Software </li></ul><ul><ul><li>Cricketgraph </li></ul></ul><ul><ul><li>Deltagraph (my personal favorite) </li></ul></ul><ul><ul><li>Microsoft graph </li></ul></ul><ul><li>PC (I don’t know)-- oh they have deltagraph!!! </li></ul><ul><li>Exploratory data analysis </li></ul><ul><ul><li>Most statistic packages have some graphing capabilities (boxplots, stem-and-leaf plots, scatterplots, etc.) S is terrific. </li></ul></ul><ul><li>High-end software (Inxight, Lucent) </li></ul>
  4. 4. Most have similar structure <ul><li>Table(s) of data </li></ul><ul><li>Choice of graph type </li></ul><ul><li>Click on columns you want to graph </li></ul><ul><li>Very simple!! </li></ul>
  5. 5. Deltagraph <ul><li>Made by SPSS </li></ul><ul><li>http://www.spss.com/software/deltagraph/ </li></ul><ul><li>Demo available </li></ul>
  6. 6. You can make beautiful graphs (from Deltagraph Web site)
  7. 7. Another Sample
  8. 8. Another one
  9. 9. More samples
  10. 10. Delta Graph: What makes it special? <ul><li>Formats available:Area,Bar,Bubble, Column, Contour, Pictograph, Pie,Scatter, Time Line, Surface,Wireframe,Histogram, Box Plot, Bullet, Organization Table. </li></ul><ul><li>Easy to use </li></ul><ul><li>Can make it fancy </li></ul>
  11. 11. Using Delta Graph <ul><li>Open Delta Graph </li></ul><ul><li>An Untlitled File will open; save as something </li></ul><ul><li>A data page will open. There are “data pages” (pages of tables) and “chart pages” that are pages with graphs on them. </li></ul><ul><li>Enter data (going downwards will be “x” axis, across will be “z” if you have 2-variable design) </li></ul>
  12. 12. Consider, for example <ul><li>Study on Perceived values of numbers (with Johanna) </li></ul><ul><li>Asked subjects to judge “how good” (on likert scale) different proportions would be, in specific contexts (a grade of 8/10, a grade of 80/100). </li></ul><ul><li>Variables </li></ul><ul><ul><li>proportion (.05-.95) </li></ul></ul><ul><ul><li>Scale (10, 100, 1000) </li></ul></ul><ul><ul><li>Context (grades, toothpaste, cancer, profits) </li></ul></ul>
  13. 13. Entering data <ul><li>We want to plot perceived goodness as a function of proportion and scale for each context (4 different graphs) </li></ul><ul><li>First thing we do is enter our data (this is like a cooking show). We have different tables for each context (Data pages). Use table icon to go to new data page. Name each page so you know what context it is. (to name page, click on “view” on menu then go to “name page”) </li></ul>
  14. 14. Making a graph <ul><li>Highlight data you want to graph </li></ul><ul><li>Click on “data” on menu page and go to “Chart Gallery” </li></ul><ul><li>Choose a chart (line graph) </li></ul><ul><li>A graph will automatically be created with certain defaults on a new “chart page” </li></ul><ul><li>Name the chart page by going to “view” and “name page” </li></ul>
  15. 15. Changing features of our graph <ul><li>Click on “text box” to add text </li></ul><ul><li>Using the chart menu </li></ul><ul><ul><li>Go to “axes” to change scale or start point, etc. </li></ul></ul><ul><ul><li>Use “labels” to label “x” and “y” axes </li></ul></ul><ul><ul><li>Use “ticks and grids” to change where your ticks are, and whether or not you have grids </li></ul></ul><ul><li>Use toolbox on left to change colors, patterns, add text, draw anything, etc. </li></ul><ul><li>Change size by pulling on corner; move </li></ul>
  16. 16. Making a new graph exactly the same <ul><li>Go to “file” menu to open up a new library </li></ul><ul><li>Drag your graph into the library and name it (you can either save as template or save w/ data). Save as template </li></ul><ul><li>Now, drag the template back to your chart page (if you want it on the same page). Or, open new chart page by clicking on graph icon and “new page” </li></ul><ul><li>It will now go to the original data page. </li></ul>
  17. 17. Making new graph continued <ul><li>Now, go to a new data page (let’s look at breast cancer page). Highlight the data you want to graph. </li></ul><ul><li>Click on plot. </li></ul><ul><li>Now a graph with same size and features appears on the page (you may have to make some changes, such as scale or labels, depending on data) </li></ul>
  18. 18. Tips for creating good graphs <ul><li>Communicate relevant information explicitly (think: What do I want to convey). Remember, different graphic formats highlight different information about the same complex data. Consider the following examples: </li></ul>
  19. 19. Look at this graph
  20. 20. Compared to this one
  21. 21. Or this one
  22. 22. Compare this graph
  23. 23. To these
  24. 24. Specific Tips <ul><li>Use line graphs for conveying trends (graphic convention is to only use for continuous data, but I violate that to make my point sometimes) </li></ul><ul><li>Bar graphs to make categorical comparisons </li></ul><ul><li>3-d graphs if exact data isn’t important, but a complex relationship or some idiosyncratic data points are important. </li></ul><ul><li>Pie charts are not good for exact values, good for comparing proportions. </li></ul>
  25. 25. Avoid forcing the reader to make any “calculations” or complex inferences <ul><li>Do not make them mentally change scale </li></ul><ul><li>Do not make them subtract everything from 100 (e.g. if you’re talking about error data in the graph and accuracy data in your paper) </li></ul><ul><li>Do not make them subtract values on one graph from another graph on a different page!! </li></ul>
  26. 26. Keep it simple <ul><li>Remember, adding 3d is not always so good. You lose ability to read exact data points, and you can occlude important data. </li></ul><ul><li>Lots of colors and designs are cool, but not necessarily helpful </li></ul><ul><li>Label your lines, avoid using legends </li></ul><ul><li>Make your symbols or lines distinct if they are to be compared. Esp if data are complex! </li></ul>
  27. 27. And plot only what you want to show <ul><li>If the 1000’s scale doesn’t matter, don’t plot it </li></ul><ul><li>If the important thing is the relative values of different contexts, plot those four averages in a single bar graph. Leave out the other variables </li></ul><ul><li>Etc. </li></ul>
  28. 28. Consider <ul><li>Goal of graph reader </li></ul><ul><li>Expertise of the graph reader </li></ul>
  29. 29. Consider some bad graphs <ul><li>Like this 3d graph of our proportion judgment study </li></ul>
  30. 30. Using graphs for more <ul><li>Exploratory data analysis </li></ul><ul><ul><li>Many statistical software packages allow you to make simple graphs to look at your data. </li></ul></ul><ul><ul><li>Some quite sophisticated </li></ul></ul><ul><li>Consider some of these high-end tools </li></ul>
  31. 31. High end software: Visualinsights Advizor
  32. 32. Inxight (xerox parc)