In the future please be a little more specific with your questions. i.e.
give us an example of your data the way it looks now and the way you want
it to look.
I think what you want is something like:
time<-seq(as.Date("2005/1/1"), as.Date("2005/1/10"),
"days")
age<-round(runif(10,30,50))
measure<-rnorm(10)
mydat<-data.frame(time=time,age=age,measure=measure) #creates a data frame
with your 3 #variables
time age measure
1 2005-01-01 48 -1.2873181
2 2005-01-02 50 0.5776001
3 2005-01-03 44 0.1892008
4 2005-01-04 38 0.4981651
5 2005-01-05 49 -1.7591745
6 2005-01-06 37 -0.8898464
7 2005-01-07 30 0.7528217
8 2005-01-08 46 -1.2421763
9 2005-01-09 39 -0.9333667
10 2005-01-10 32 1.2086509
#suppose you only want patients older than 40
Older40<-mydat[age>=40,c(1,3)]
time measure
1 2005-01-01 -1.2873181
2 2005-01-02 0.5776001
3 2005-01-03 0.1892008
5 2005-01-05 -1.7591745
8 2005-01-08 -1.2421763
Is this what you wanted to do?
Francisco
>From: "" <combe at b3e.jussieu.fr>
>To: "" <R-help at stat.math.ethz.ch>
>Subject: [R] he^lp on "stack" function
>Date: Thu, 3 Feb 2005 18:10:24 +0100
>
>
>
>
>Excuse me.
>I don't understant how to use the function "stack".
>I'm not sure to know the good syntax.
>
>I've got a data witch column names are the time when the mesures was
done
>and
>an
>other who indicates the age of the subjetcs.
>I would like to do a new matrix with patients older than a value and the
>new
>matrix will contain in the first column the time of the mesures and in the
>second th evalue of the mesure.
>
>Could you help me please ?
>
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