Here's another example of my plotmath whipping boy, the Normal distribution.
A colleague asks for a Normal plotted above a series of axes that represent various other distributions (T, etc). I want to use vectors of equations in plotmath to do this, but have run into trouble. Now I've isolated the problem down to a relatively small piece of working example code (below). If you would please run this, I think you will see the problem. When plotmath meets one vector of expressions, it converts all but one to math, so in the figure output i get, in LaTeX speak b1 $\mu-1.0 \sigma$ $\mu$ All values except the first come out correctly. This happens only when I try to use bquote or substitute to get variables to fill in where the 1.96, 1.0, and so forth should be. In the figure output, you should see a second axis where all of the symbols are resolved correctly. As usual, thanks in advance for your help, sorry if I've made an obvious mistake or overlooked a manual. ### Filename: plotMathProblem.R ### Paul Johnson July 5, 2010 ### email me <paulj...@ku.edu> sigma <- 10.0 mu <- 4.0 myx <- seq( mu - 3.5*sigma, mu+ 3.5*sigma, length.out=500) myDensity <- dnorm(myx,mean=mu,sd=sigma) ### xpd needed to allow writing outside strict box of graph ### Need big bottom margin to add several x axes par(xpd=TRUE, ps=10, mar=c(18,2,2,2)) plot(myx, myDensity, type="l", xlab="", ylab="Probability Density ", main=myTitle1, axes=FALSE) axis(2, pos= mu - 3.6*sigma) axis(1, pos=0) lines(c(myx[1],myx[length(myx)]),c(0,0)) ### closes off axes addInteriorLine <- function(x, m, sd){ for (i in 1:(length(x))){ lines( c(x[i],x[i]), c(0, dnorm(x[i],m=m,sd=sd)), lty= 14, lwd=.2) } } dividers <- c(qnorm(0.025), -1, 0, 1, qnorm(0.975)) addInteriorLine(mu+sigma*dividers, mu,sigma) # bquote creates an expression that text plotters can use t1 <- bquote( mu== .(mu)) mtext(bquote( mu == .(mu)), 1, at=mu, line=-1) addInteriorLabel <- function(pos1, pos2, m, s){ area <- abs(100*( pnorm(m+pos1*s,m,s)-pnorm(m+pos2*s, m,s))) mid <- m+0.5*(pos1+pos2)*s text(mid, 0.5*dnorm(mid,m,s),label=paste(round(area,2),"%")) } addInteriorLabel(dividers[1],dividers[2], mu, sigma) addInteriorLabel(dividers[2],dividers[3], mu, sigma) addInteriorLabel(dividers[3],dividers[4], mu, sigma) addInteriorLabel(dividers[4],dividers[5], mu, sigma) ### Following is problem point: axis will ### end up with correct labels, except for first point, ### where we end up with "b1" instead of "mu - 1.96*sigma". b1 <- substitute( mu - d*sigma, list(d=round(dividers[1],2)) ) b2 <- substitute( mu - sigma ) b3 <- substitute( mu ) b4 <- substitute( mu + sigma ) b5 <- substitute( mu + d*sigma, list(d=round(dividers[5],2)) ) ## plot(-20:50,-20:50,type="n",axes=F) axis(1, line=4,at=mu+dividers*sigma, labels=c(expression(b1),b2,b3,b4,b5), padj=-1) ### This gets "right result" but have to hard code the dividers b1 <- expression( mu - 1.96*sigma ) b2 <- expression( mu - sigma ) b3 <- expression( mu ) b4 <- expression( mu + sigma ) b5 <- expression( mu + 1.96*sigma ) axis(1, line=8,at=mu+dividers*sigma, labels=c(b1,b2,b3,b4,b5), padj=-1) -- Paul E. Johnson Professor, Political Science 1541 Lilac Lane, Room 504 University of Kansas ______________________________________________ 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.