Plot question

I have some data consisting of multiple trials of an experiment with 
different values of an independent variable.  If I run
R> plot(var,result)
I get a scatterplot of result versus the independent variable var.
If I run
R> plot(as.factor(var),result)
I get a boxplot of the distribution of result for each value of var.  In 
this plot, each boxplot is labeled by the corresponding value of var, 
but the absissas are evenly spaced.
Is it possible to generate a boxplot with the absissas of each boxplot 
equal to the corresponding value of var?

Alan Barnett, PhD
Imaging Physicist
National Institutes of Health
NIMH/CBDB
301 402 3507