Perfect. Thank you. -Mitch
-----Original Message----- From: Dimitris Rizopoulos [mailto:d.rizopou...@erasmusmc.nl] Sent: Tuesday, May 17, 2011 9:51 AM To: Downey, Patrick Cc: r-help@r-project.org Subject: Re: [R] Minimum value by ID 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@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/ ______________________________________________ R-help@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.
