[R] factor to numeric in data.frame

From: Heinz Tuechler <tuechler_at_gmx.at>
Date: Sat 02 Apr 2005 - 21:01:57 EST

Dear All,

Assume I have a data.frame that contains also factors and I would like to get another data.frame containing the factors as numeric vectors, to apply functions like sapply(..., median) on them. I read the warning concerning as.numeric or unclass, but in my case this makes sense, because the factor levels are properly ordered. I can do it, if I write for each single column "unclass(...), but I would like to use indexing, e.g. unclass(df[1:10]). Is that possible?

Heinz Tüchler

## Example:

f1 <- factor(c(rep('c1-low',2),rep('c2-med',5),rep('c3-high',3))) f2 <- factor(c(rep('c1-low',5),rep('c2-low',3),rep('c3-low',2)))
df.f12 <- data.frame(f1,f2) # data.frame containing factors

## this does work

df.f12.num <- data.frame(unclass(df.f12[[1]]),unclass(df.f12[[2]])) df.f12.num
## this does not work
df.f12.num <- data.frame(unclass(df.f12[[1:2]])) df.f12.num
## this does not work
df.f12.num <- data.frame(unclass(df.f12[1:2])) df.f12.num

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