Two other options (which I prefer):
aggregate(x~id.var, data=dat, FUN=min)
or
library(doBy)
summaryBy(x~id.var, data=dat, FUN=min)
HTH,
Ivan
Le 5/17/2011 16:09, John Kane a écrit :
A bit convolulted but it works
library(reshape2)
yy<- melt(dat)
zz<- cast(yy, id.var ~ variable, min)
zz[,2]
--- On Tue, 5/17/11, Downey, Patrick<pdow...@urban.org> wrote:
From: Downey, Patrick<pdow...@urban.org>
Subject: [R] Minimum value by ID
To: r-help@r-project.org
Received: Tuesday, May 17, 2011, 9:44 AM
Hello,
I have a longitudinal dataset where each individual has a
different number
of entries. Thus, it is of the following structure:
x<- runif(12)
id.var<-
factor(c(rep("D1",4),rep("D2",2),rep("D3",3),rep("D4",3)))
dat<- as.data.frame(x)
dat$id.var<- id.var
dat
dat
x
id.var
1 0.9611269 D1
2 0.6738606 D1
3 0.9724301 D1
4 0.9787778 D1
5 0.2468355 D2
6 0.7031734 D2
7 0.2458727 D3
8 0.8439799 D3
9 0.5223196 D3
10 0.6930475 D4
11 0.8887677 D4
12 0.5483756 D4
I want to create a vector with length equal to the number
of unique id.var
and which has the minimum value for each id.var. That is, I
want a vector
which holds the minimum value for each person in my
dataset.
The following works, but I'm sure there is something more
efficient. I
would assume there is a function for this, but couldn't
find anything.
id<- levels(id.var)
min<- rep(0,length(id))
for(i in 1:length(id)){
min[i]<- min(dat$x[dat$id.var==id[i]])
}
min
min
[1] 0.6738606 0.2468355 0.2458727 0.5483756
Thank you in advance,
Mitch
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--
Ivan CALANDRA
PhD Student
University of Hamburg
Biozentrum Grindel und Zoologisches Museum
Dept. Mammalogy
Martin-Luther-King-Platz 3
D-20146 Hamburg, GERMANY
+49(0)40 42838 6231
ivan.calan...@uni-hamburg.de
**********
http://www.for771.uni-bonn.de
http://webapp5.rrz.uni-hamburg.de/mammals/eng/1525_8_1.php
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