Rutgers University - Center for Vector Biology Graphing Data: Have I Got a Story to Tell… Lisa Reed, Ph.D Center for Vector Biology Rutgers University 26 April 2012

Rutgers University - Center for Vector Biology For Today Graph Importance Examples, both good and bad What are good graphs and good graph rules How do you make a good graph –Excel graph designs –Others How to get them from Excel to Word

Rutgers University - Center for Vector Biology “The greatest value of a picture is when it forces us to notice what we never expected to see.” Tukey, 1977, Exploratory Data Analysis

Rutgers University - Center for Vector Biology Why Are Graphs Important? Can give information quickly Can highlight the point you want to make Can direct towards statistical tools But can give misinformation if not careful

Rutgers University - Center for Vector Biology Napoleon’s March to and From Moscow by Minard Shows number of troops in geography and travel Shows temperature and time Gives an understanding for Napoleon’s failure

Rutgers University - Center for Vector Biology Snow’s Cholera Well Identifies cholera deaths (in red) Identifies wells (in blue) Implicates cholera as a water-borne disease Clearly indicates which well should be shut down.

Rutgers University - Center for Vector Biology Simple Statistical Graphs

Rutgers University - Center for Vector Biology Not so good. From junkcharts.typepad.com

Rutgers University - Center for Vector Biology What Makes A Good Graph? Simple and efficient: Presents one basic conclusion. Clear and Unambiguous: You understand what is being presented. Not Misleading: You don’t come to a wrong conclusion. Meaningful: You come to a correct and relevant conclusion.

Rutgers University - Center for Vector Biology Achieving Good Graphics Use Titles – What are you trying to show? Use Axis Labels – Tell what you are graphing. Use Units of Measurements – Tell what you are graphing. Use legends. Use Series coloration/fills – but be careful for those who are colorblind. Keep scaling appropriate. Write out equations when appropriate. Use error bars when available.

Rutgers University - Center for Vector Biology Use Titles, Labels, Units of Measure, Legends

Rutgers University - Center for Vector Biology Fills & Colorblindness Patterns (but must load patterns if using Excel 2007) Labels 1 Color and Brightness Grayscale

Rutgers University - Center for Vector Biology You can run a colorblind checker… /vischeck/vischeckImage. phphttp:// /vischeck/vischeckImage. php Browse to your image and run the checker.

Rutgers University - Center for Vector Biology Scale Generally begin at zero. But look at data. If more than 1 graph on a page, try to use same scale. If you cannot use one scale, make it obvious that the scales differ. –Different colors –Different gridlines

Rutgers University - Center for Vector Biology Equations and Error Bars Both elements give added information. But need specific information –Regression lines need the equation AND the R 2 –Error bars need the type.

Rutgers University - Center for Vector Biology Making Graphs in Excel Highlight Data Choose Graph Style… Voila!

Rutgers University - Center for Vector Biology Editing Graphs in Excel

Rutgers University - Center for Vector Biology Changing Chart Types

Rutgers University - Center for Vector Biology Switch Row/Column

Rutgers University - Center for Vector Biology Adding Titles, Labels and Legends Hold Down the Alt key and type from the keypad numbers: Alt 241 = ± Alt 248 = °

Rutgers University - Center for Vector Biology No Fills Available for versions 2007! But, download add-in – et/excel/PatternUI.z iphttp://officeblogs.n et/excel/PatternUI.z ip Unzip file (and remember where it is) Go to Window Flower, Excel Options, Add-in, Go and click Patternui. Click on series in graph, go to Chart Tools, Format, Patterns and select which one you want.

Rutgers University - Center for Vector Biology Scale Generally begin at zero. But look at data. If more than 1 graph on a page, try to use same scale. If you cannot use one scale, make it obvious that the scales differ. –Different colors –Different gridlines

Rutgers University - Center for Vector Biology Equations

Rutgers University - Center for Vector Biology The Agony and the Ecstasy of Error Bars You have a set of data. You do a pivot table to summarize average and SD. You plot average with the intention of doing SD as error bars: You have a set of data. You do a pivot table to summarize average and SD. You copy and paste values, THEN create your graph: X

Rutgers University - Center for Vector Biology Achieving Good Graphics Use Titles Use Axis Labels Use Units of Measurements Use legends. Use series coloration/fills. Keep scaling appropriate. Write out equations when appropriate. Use error bars when available.

Rutgers University - Center for Vector Biology Why this Class? Resistance Classes Graphs Simple Statistics Probit Analysis

Rutgers University - Center for Vector Biology Suggested References The Visual Display of Quantitative Information – Edward Tufte, 1983 How to Lie with Statistics – Darrell Huff, 1994