Andrew Robinson wrote:
Greetings R community,
I am curious about the following behaviour: if I define a factor, and then store a subset of it in a list, the stored version seems to drop levels that were not included in the subset. E.g. ..
mask <- c(T, F) grp.1 <- factor(c(1,2)) list(grp.1)
[[1]] [1] 1 2 Levels: 1 2
list(grp.1[mask])
[[1]] [1] 1 Levels: 1
It is as though the list were redefining the factor and dropping empty levels. I would like to keep them (I am using the list for a two-dimensional tapply). Is there any way to avoid this?
I'm using R 2.0.0 on FreeBSD 5.2.1.
Thanks,
Andrew
Andrew,
I cannot replicate this with R-2.0.0 patched on Win2000Pro:
> mask <- c(T, F) > grp.1 <- factor(c(1,2)) > list(grp.1) [[1]] [1] 1 2 Levels: 1 2
> grp.1[mask] [1] 1 Levels: 1 2 > list(grp.1[mask]) [[1]] [1] 1 Levels: 1 2
--sundar
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