Create a boxplot in R that labels a box with the sample size (N)

Is there a way to create a boxplot in R that will display with the box (somewhere) an "N=(sample size)"? The varwidth logical adjusts the width of the box on the basis of sample size, but that doesn't allow comparisons between different plots.

FWIW, I am using the boxplot command in the following fashion, where 'f1' is a factor:

boxplot(xvar ~ f1, data=frame, xlab="input values", horizontal=TRUE)

A:

Here's some ggplot2 code. It's going to display the sample size at the sample mean, making the label multifunctional!
First, a simple function for fun.data
give.n <- function(x){
   return(c(y = mean(x), label = length(x)))
}
Now, to demonstrate with the diamonds data
ggplot(diamonds, aes(cut, price)) + 
   geom_boxplot() + 
   stat_summary(fun.data = give.n, geom = "text")
You may have to play with the text size to make it look good, but now you have a label for the sample size which also gives a sense of the skew.
A2:
You can use the names parameter to write the n next to each factor name.
If you don't want to calculate the n yourself you could use this little trick:
# Do the boxplot but do not show it
b <- boxplot(xvar ~ f1, data=frame, plot=0)
# Now b$n holds the counts for each factor, we're going to write them in names
boxplot(xvar ~ f1, data=frame, xlab="input values", names=paste(b$names, "(n=", b$n, ")"))

http://stackoverflow.com/questions/3483203/create-a-boxplot-in-r-that-labels-a-box-with-the-sample-size-n