[R] for loops and counter interpolation

[e.rapsomaniki at mail.cryst.bbk.ac.uk]

Hi

I'm sorry about the triviality of my problem. I have a vector (v) of three
columns (logA, logB, id). I want to compute (and plot) the correlation between
logA and logB for different thresholds of id (e.g. >30, etc). So I tried:

for(i in 1:100){
   points(cor(v$logA[v$id>i], v$logB[v$id>i], use="complete.obs"), i))
}
(i created a plot object already)

but it comes with the error: x is empty, ie it doesn't interpolate the value of
i in the for loop into the vector selection.

Does anyone know if there's any better way of doing this? 

Many Thanks
Eleni Rapsomaniki
Birkbeck College, UK