On 07/07/10 06:03, Paul Johnson wrote:
> [...]
> Hi, Duncan and David
>
> Thanks for looking. I suspect from the comment you did not run the
> code. The expression examples I give do work fine already. But I
> have to explicitly put in values like 1.96 to make them work. I'm
> trying to avid that with substitute, which does work for b2, b3, b4,
> b5, all but b1. Why just one?
>
> I'm uploading a picture of it so you can see for yourself:
>
> http://pj.freefaculty.org/R/plotmathwrong.pdf
>
> please look in the middle axis.
>
> Why does only b1 not work, but the rest do?
>
>
Because you only had one (as.)expression in your original code,
perhaps? This version works for me:
### Filename: plotMathProblem.R
### Paul Johnson July 5, 2010
### email me<paulj...@ku.edu>
### 2010-07-06 AE : Changes.
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=*as.expression(c(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)
Allan
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