[R] long format - find age when another variable is first 'high'
3.14david at gmail.com
Mon May 25 14:45:01 CEST 2009
I've got a data frame with children examined multiple times and at various
ages. I'm trying to find the first age at which another variable
(LDL-Cholesterol) is >= 130 mg/dL; for some children, this may never happen.
I can do this with transformBy and ddply, but with 10,000 different
children, these functions take some time on my PCs - is there a faster way
to do this in R? My code on a small dataset follows.
Thanks very much, David Freedman
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