Graphing Your Data: Graphing Software and Other TipsPriti Shah

GoalsCommunicating an important quantitative fact (e.g. an interaction) to an audience (talk, journal article)Exploratory Data analysis (trying to figure out what your data say

Software optionsMacintosh SoftwareCricketgraphDeltagraph (my personal favorite)Microsoft graphPC (I dont know)-- oh they have deltagraph!!!Exploratory data analysisMost statistic packages have some graphing capabilities (boxplots, stem-and-leaf plots, scatterplots, etc.) S is terrific.High-end software (Inxight, Lucent)

Most have similar structureTable(s) of dataChoice of graph typeClick on columns you want to graphVery simple!!

DeltagraphMade by SPSShttp://www.spss.com/software/deltagraph/Demo available

You can make beautiful graphs (from Deltagraph Web site)

Another Sample

Another one

More samples

Delta Graph: What makes it special?Formats available:Area,Bar,Bubble, Column, Contour, Pictograph, Pie,Scatter, Time Line, Surface,Wireframe,Histogram, Box Plot, Bullet, Organization Table. Easy to useCan make it fancy

Using Delta GraphOpen Delta GraphAn Untlitled File will open; save as somethingA data page will open. There are data pages (pages of tables) and chart pages that are pages with graphs on them.Enter data (going downwards will be x axis, across will be z if you have 2-variable design)

Consider, for exampleStudy on Perceived values of numbers (with Johanna)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). Variablesproportion (.05-.95)Scale (10, 100, 1000)Context (grades, toothpaste, cancer, profits)

Entering dataWe want to plot perceived goodness as a function of proportion and scale for each context (4 different graphs)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)

Making a graphHighlight data you want to graphClick on data on menu page and go to Chart GalleryChoose a chart (line graph)A graph will automatically be created with certain defaults on a new chart page Name the chart page by going to view and name page

Changing features of our graphClick on text box to add textUsing the chart menuGo to axes to change scale or start point, etc.Use labels to label x and y axesUse ticks and grids to change where your ticks are, and whether or not you have gridsUse toolbox on left to change colors, patterns, add text, draw anything, etc.Change size by pulling on corner; move

Making a new graph exactly the sameGo to file menu to open up a new libraryDrag your graph into the library and name it (you can either save as template or save w/ data). Save as templateNow, 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 pageIt will now go to the original data page.

Making new graph continuedNow, go to a new data page (lets look at breast cancer page). Highlight the data you want to graph.Click on plot.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)

Tips for creating good graphsCommunicate 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:

Look at this graph

Compared to this one

Or this one

Compare this graph

To these

Specific TipsUse line graphs for conveying trends (graphic convention is to only use for continuous data, but I violate that to make my point sometimes)Bar graphs to make categorical comparisons3-d graphs if exact data isnt important, but a complex relationship or some idiosyncratic data points are important. Pie charts are not good for exact values, good for comparing proportions.

Avoid forcing the reader to make any calculations or complex inferencesDo not make them mentally change scaleDo not make them subtract everything from 100 (e.g. if youre talking about error data in the graph and accuracy data in your paper)Do not make them subtract values on one graph from another graph on a different page!!

Keep it simpleRemember, adding 3d is not always so good. You lose ability to read exact data points, and you can occlude important data.Lots of colors and designs are cool, but not necessarily helpfulLabel your lines, avoid using legendsMake your symbols or lines distinct if they are to be compared. Esp if data are complex!

And plot only what you want to showIf the 1000s scale doesnt matter, dont plot itIf the important thing is the relative values of different contexts, plot those four averages in a single bar graph. Leave out the other variablesEtc.

ConsiderGoal of graph readerExpertise of the graph reader

Consider some bad graphsLike this 3d graph of our proportion judgment study

Using graphs for moreExploratory data analysisMany statistical software packages allow you to make simple graphs to look at your data. Some quite sophisticatedConsider some of these high-end tools

High end software:Visualinsights Advizor

Inxight (xerox parc)