R listers: I have been foiled by plotmath!
(in R 2.01,Windows 2000) The task: Plot a normal density and label the ticks as mu - 3 sigma, mu - 2 sigma, ...., mu + 3 sigma, where the mu's and sigmas appear as Greek symbols, of course. The following code does this: x<-seq(-3,to=3,by=.01) y<-dnorm(x) plot(x,y,type='h',col='lightblue',axes=FALSE) lines(x,y,col='darkblue') axis(2) for(i in seq(-3,to=3)) axis(1,at=i, lab=switch(sign(i)+2, eval(substitute(expression(mu-j*sigma),list(j=-i))), expression(mu), eval(substitute(expression(mu+j*sigma),list(j=i))))) box() However, I think the code in the for loop is ugly and probably means that I'm doing it wrong. In particular: 1) Is there a neat way to use one axis() call and a vector (of expressions?) for the lab=argument? 2) The plotmath Help state that expressions can be used for axis labels, so I would have expected the above to work without the eval()call -- but it does not. Would someone kindly explain to me why not -- i.e., what I have misunderstood. That is, to be clear, why does the following not work: for(i in seq(-3,to=3)) axis(1,at=i, lab=switch(sign(i)+2, substitute(expression(mu-j*sigma),list(j=i)), expression(mu), substitute(expression(mu+j*sigma),list(j=i)))) Any further ideas,insights, or pointers to reference materials would also be appreciated. Many thanks. -- Bert Gunter Genentech Non-Clinical Statistics South San Francisco, CA "The business of the statistician is to catalyze the scientific learning process." - George E. P. Box ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html