[R] Variables captured in closures get copied?
Titus von der Malsburg
malsburg at gmail.com
Wed Feb 11 18:09:05 CET 2009
Hi list! I have a data frame called fix and a list of index vectors
> head(rois, 3)
 2 1
 6 7 28 26 27 24 25
The part that's causing the issue is the following line:
lapply(rois, function(roi) fix$x[roi] <- 100)
So for every index vector I'd like to set the respective entries in the
data frame (fix) to 100.
I expected the data frame would be changed after lapply but instead it
remains unchanged. I understand that when I pass an argument into a
function it gets passed as a value and not as a reference. But here fix
is not an argument but captured in the closure. Do my questions are:
What's going on here and what is the idiomatic way of achieving my goal?
Thanks for any help!
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