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$id.var==id[i]])
}
min
> min
[1] 0.6738606 0.2468355 0.2458727 0.5483756
Thank you in advance,
Mitch
have a look at help file of function tapply(), and try this: with(dat, tapply(x, id.var, min)) I hope it helps. Best, Dimitris On 5/17/2011 3:44 PM, Downey, Patrick wrote:> Hello, > > I have a longitudinal dataset where each individual has a different number > of entries. Thus, it is of the following structure: > > x<- runif(12) > id.var<- factor(c(rep("D1",4),rep("D2",2),rep("D3",3),rep("D4",3))) > dat<- as.data.frame(x) > dat$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 > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >-- Dimitris Rizopoulos Assistant Professor Department of Biostatistics Erasmus University Medical Center Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands Tel: +31/(0)10/7043478 Fax: +31/(0)10/7043014 Web: http://www.erasmusmc.nl/biostatistiek/
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 <PDowney at urban.org> wrote:> From: Downey, Patrick <PDowney at urban.org> > Subject: [R] Minimum value by ID > To: r-help at 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 > > ______________________________________________ > R-help at r-project.org > mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, > reproducible code. >