hello! i need help for a specific graphic issue

hi Giacomo,

consider this:

means<-c(4,6,8)
stand.error<-c(0.1,0.3,0.5)
lowlim<-means-stand.error
uplim<-means+stand.error
plot(as.factor(c("a","b","c")),means,ylim=c(min(lowlim),max(uplim)))
arrows(c(1:3),lowlim,c(1:3),uplim,code=3,angle=90)

Still, its just a workaround and I don't think you can get rid of the horizontal mean-lines because this is actually a box-plot.
Otherwise you could try the 'errbar()' from the Hmisc package. I never used that, but maybe it works.
Generally, if you have problems with plot-dimensions, you can get instant information with 'locator()', which returns coordinates of mouse clicked locations in plots.

cheers, /ren?