On Mar 21, 2011, at 5:25 AM, Marcel Curlin wrote:
Hello,
I have a large dataset of the form
subj var1 var2
001 100 200
001 120 226
001 130 238
001 140 245
001 150 300
002 110 205
002 125 209
003 101 233
003 115 254
I would like to perform linear regression of var2 on var1 for each
subject
separately. It seems like I should be able to use the tapply
function as you
do for simple operations (like finding a mean of var1 for each
subject), but
I am not sure of the correct syntax for this. Is there a way to do
this?
tapply works on vectors, split works on data.frames.
lapply(split(dat, dat$subj), function(x) lm(var2 ~ var1, data=x))
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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