On Jan 11, 2010, at 7:58 PM, JustinNabble wrote:
I'd like to get a long data set of minimum values from groups in
another data
set.
The following almost does what I want. (Note, I'm using the word
factor
differently from it's meaning in R; bad choice of words)
myframe = data.frame(factor1 = rep(1:2,each=8), factor2 =
rep(c("a","b"),each=4, times=2), factor3 = rep(c("x","y"),each=2,
times=4),
y=1:16)
attach(myframe)
# with(myframe, ....) would be a better construction
minimums = by(y, list(factor1, factor2,factor3), min)
detach(myframe)
It's a table, which IS like an array, You want:
> as.data.frame.table(minimums)
Var1 Var2 Var3 Freq
1 1 a x 1
2 2 a x 9
3 1 b x 5
4 2 b x 13
5 1 a y 3
6 2 a y 11
7 1 b y 7
8 2 b y 15
The problem is that "minimums" is object of class "by", which looks
like
some kind of array with the number of dimension equal to the number of
factors. I just want two dimensions though, with factors in columns.
I can't
figure out how to reformat it to something like this:
factor1 factor2 factor2 y
1 a x 1
2 a x 9
1 b x 5
...
I could make nested for loops, but I'd like something that will work
for an
arbitrary number of factors. I've seen some functions that will
rearrange
data (e.g. reshape), but they all seem to require a data.frame to
start
with.
--
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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