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)
