[R] Error bars on barplots for only particular bars

[kellys17]

Hi,

  I have a data set that has columns "bird.species", "tree.species"and
"count". I am investigating differences in tree species usge by two species
of birds. "Count" is numerical and is a count of observations of bird
species x using tree species x. For bird species A I have 3 different counts
for each tree species. For bird species B I have only 1 count for each tree
species. 

I have generated a barplot using the following function:
barplot(tapply(count,list(bird.species,tree.species),mean),beside=TRUE)

This graph is so far ok and gives the mean count for bird species A.
I want to add error bars to illustrate the variance in mean of bird species
A for each tree species.

The error bar function I am using is:
error.bars<-function(yv,z,nn){
xv<-barplot(yv,ylim=c(0,(max(yv)+max(z))),names=nn,
ylab=deparse(substitute(yv)))
g<-(max(xv)-min(xv))/50
for (i in 1:length(xv)){lines(c(xv[i],xv[i]),c(yv[i]+z[i],yv[i]-z[i]))
lines(c(xv[i]-g,xv[i]+g),c(yv[i]+z[i],yv[i]+z[i]))
lines(c(xv[i]-g,xv[i]+g),c(yv[i]-z[i],yv[i]-z[i]))}}

I used "error.bars(ybar1,se1,labels1)" to try generate the error bars with
se1<-rep("standard error of a mean", "no. of numbers used to calculate
mean")
labels1<-as.character(levels(tree.species))
ybar1<-as.vector(tapply(count,tree.species,mean))

but the it failed and the resulting warning I got was:
Error in barplot.default(yv, ylim = c(0, (max(yv) + max(z))), names = nn,  : 
  incorrect number of names

I was wondering If anyone could help with me this warning, or point me in
the right direction as to how to illustrate the variance in means from bird
species A without adding any error bars to bird species B (which has no
variance to show)?

Any help is very much appreciated,

 Thanks,

  Seán Kelly.
-- 
View this message in context: http://n4.nabble.com/Error-bars-on-barplots-for-only-particular-bars-tp1014284p1014284.html
Sent from the R help mailing list archive at Nabble.com.