Uses and abuses of logarithmic axes - GraphPad Software

More documents

Recommendations

Info

Logarithmic axes on bar graphs are misleadingThewholepointofabargraphisthattherelativeheightofthebarstellsyouabouttherelativevaluesplotted.Inthegraphbelow,onebarisfourtimesastallastheotherandonevalue(800)isfourtimestheother(200). 4
Sincezerocan’tbeshownonalogaxis,thechoiceofastartingplaceisarbitrary.Accordingly,therelativeheightoftwobarsisnotdirectlyrelatedtotheirrelativevalues.Thegraphsbelowshowthesamedataasthegraphabove,butwiththreedifferentchoicesforwheretheaxisbegins.Thisarbitrarychoiceinfluencestherelativeheightofthetwobars,amplifiedinthegraphontheleftandminimizedinthegraphontheright.Ifthegoalistocreatepropaganda,abargraphusingalogarithmicaxisisagreattool,asitletsyoueitherexaggeratedifferencesbetweengroupsorminimizethem.Allyouhavetodoiscarefullychoosetherangeofyouraxis.Don’tcreatebargraphsusingalogarithmicaxisifyourgoalistohonestlyshowthedata.When to use a logarithmic axisA logarithmic X axis is useful when the X values are logarithmically spacedTheX‐axisusuallyplotstheindependentvariable–thevariableyoucontrol.IfyouchoseXvaluesthatareconstantratios,ratherthanconstantdifferences,thegraphwillbeeasiertoviewonalogarithmicaxis.Thetwographsbelowshowthesamedata.Xisdose,andYisresponse.Thedoseswerechosensoeachdoseistwicethepreviousdose.Whenplottedwithalinearaxis(left)manyofthevaluesaresuperimposedanditishardtoseewhat’sgoingon. 5
Page 1 and 2: The Use and Abuse of Logarithmic Ax
Page 3: GraphPadPrismcanplotlog2axes.Choose
Page 7 and 8: axis,thevalueplottedontheYaxisequal
Page 9 and 10: Whenshownonalinearscale(graphonthel
Page 11 and 12: Distinguish using a logarithmic axi
Page 13: ange(0to5).Thefirstaxishasdecimalnu

Uses and abuses of logarithmic axes - GraphPad Software

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?