[R] remove levels from a factor

[Frank E Harrell Jr]

Adrian Dusa wrote:
> Adrian Dusa <dusa.adrian <at> gmail.com> writes:
>>> [...snip...]
>>> f[which(f %in% names(table(f))[table(f) >= 2]), drop=TRUE]
>> [1] a a
>> Levels: a
> 
> Or, more simple:
> 
>> f[f %in% names(table(f))[table(f) >= 2], drop=TRUE]
> [1] a a
> Levels: a
> 
> Adrian

Also see the combine.levels function in the Hmisc package.
Frank

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-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University