a <- data.frame(b = rep(1:5, each=2), c=factor(rep("a",10), levels=c("a","b"))) levels(subset(a, b=1, drop=T)$c) # [1] "a" "b"
Is this a bug?
Thanks,,
Hadley
This is always controversial. I am apparently in the small minority in believing that the default behavior is what you are wishing for. That's why the Hmisc package by default drops unused levels (but allows you to override that with options(drop.unused.levels=FALSE). It is distasteful to have to override system behavior but I felt I had to in this case. No one in R-core wanted to add a non-default option to R e.g. options(drop.unused.levels=TRUE).
Frank
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Frank E Harrell Jr Professor and Chair School of Medicine
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