[R] How do I coerce numeric factor columns of data frame to vector?
Michael A. Miller
mmiller3 at iupui.edu
Tue Sep 9 17:01:58 CEST 2003
>>>>> "Thomas" == Thomas W Blackwell <tblackw at umich.edu> writes:
> Michael - Because these columns are factors to begin with,
> using as.numeric() alone will have unexpected results. See
> the section "Warning:" in help("factor").
Ah, thanks for pointing that out. When I've used as.numeric on
factors, it is usually because I've explicitly made a numeric
variable a factor. I can see where something that I think aught
to be numeric would be interpreted as a factor, say due to an
error in formatting an input file. If I do something like this:
x <- some numeric array
f <- factor(x)
y <- as.numeric(x)
is there a possibility of y not equalling x? If x really is
numeric that is.
Michael A. Miller mmiller3 at iupui.edu
Imaging Sciences, Department of Radiology, IU School of Medicine
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