[R] ggplot2 - expand range?

[Pedro de Barros]

Dear UserRs,

I am trying to use systematically ggplot2 for most of my plots, but I 
am fighting some lack of documentation, which I try to overcome.

I want to build a scatterplot where the axes cross exactly at (0,0). 
I tried using scale_y_continuous(limits=c(0,10)), but I always get an 
extra space at the bottom of the axes. The code I used is below.

  > plotdata<-data.frame(x=1:10, y=runif(10))
  > plot<-ggplot()
  > plot<-plot+layer(data=plotdata, mapping=aes_string(x='x',y='y'),
geom='point', stat='identity', size=4)
  > plot<-plot+ scale_y_continuous(limits=c(0,1))
  > print(plot)

I believe there may be a way to use expand_range to fix this (I think 
I read about it somewhere), but I do not seem to find out how.
I have searched the ggplot help and
the archives, but cannot find the answer to this issue.
I would really appreciate if anyone could give me a pointer.

I am using R2.6.0 (patched) on Windows

Thanks,
Pedro