On 9/29/07, Michael Friendly <[EMAIL PROTECTED]> wrote: > > hadley wickham wrote: > >> > > I was interested to see that you have code for drawing scatterplots > > with multiple y-axes. As far as I know the only legitimate use for a > > double-axis plot is to confuse or mislead the reader (and this is not > > a very ethical use case). Perhaps you have a counter-example? > > > > Hadley > > > While it is true that the double-Y-axis graph is generally considered > sinful, it can be used effectively to show the relation of two time > series in ways that other graphs can't do as well. > > For one striking example, > a political, presentation graphic, see: > http://www.math.yorku.ca/SCS/Gallery/images/commonsenserevolution6.pdf > described on my Graphical Excellence page, > http://www.math.yorku.ca/SCS/Gallery/excellence.html > I found it easy to excuse the sin by the 'wow effect' produced by the > graph.
While I agree that the double y-axis plot can be used to compare two time series, I'm not sure whether or not it actually is effective. The appearance of the display is so critically dependent on the relative scales of the axes, that it is easy to draw the wrong conclusion. Why not use a scatterplot or path plot (i.e. connect subsequent observations with edges) if you want to understand the relationship between two variables? >From a aesthetic perspective, the common sense revolution graphic is clearly a success, being both striking and attractive, but I think it fails statistically, by making it hard to accurately assess the relationship between the two variables. Hadley -- http://had.co.nz/ ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
