Titus von der Malsburg wrote:
Hi list! I have a data frame called fix and a list of index vectors
called rois:
> head(rois, 3)
[[1]]
[1] 2 1
[[2]]
[1] 3
[[3]]
[1] 6 7 28 26 27 24 25
The part that's causing the issue is the following line:
lapply(rois, function(roi) fix$x[roi] <- 100)
So for every index vector I'd like to set the respective entries in the
data frame (fix) to 100.
I expected the data frame would be changed after lapply but instead it
remains unchanged. I understand that when I pass an argument into a
function it gets passed as a value and not as a reference. But here fix
is not an argument but captured in the closure. Do my questions are:
What's going on here and what is the idiomatic way of achieving my goal?
It's a local variable in the function. Not in principle different from
function(roi) { fix <- fix ; ... }
You could use superassignment (<<-), but a simpler idiom is
for (roi in rois) fix$x[roi] <- 100
--
O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B
c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalga...@biostat.ku.dk) FAX: (+45) 35327907
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