oh! and if you want to be less ad-hoc: sapply(test, function(x) x[,2])
b On Jul 22, 2007, at 3:50 PM, Benilton Carvalho wrote: > test <- lapply(1:3, function(i) cbind(runif(15), rnorm(15,2))) > sapply(test, "[", 16:30) > > b > > On Jul 22, 2007, at 3:39 PM, [EMAIL PROTECTED] wrote: > >> Hello, >> >> I think I have a mental block when it comes to working with >> lists. lapply and sapply appear to do some magical things, but I >> can't seem to master their usage. >> >> As an example, I would like to convert a column within a list to a >> matrix, with the list element corresponding to the new matrix column. >> >> #Here is a simplified example: . >> test=vector("list", 3) >> for (i in 1:3){ test[[i]]=cbind(runif(15), rnorm(15,2)) } #create >> example list (I'm sure there is a better way to do this too). >> >> #Now, I wan to get the second column back out, converting it from >> a list to a matrix. This works, but gets confusing/inefficient >> when I have multiple complex lists I am trying to manage. >> >> savecol2=matrix(0,15,0) >> for (i in 1:3){ >> savecol2=cbind(savecol2, test[[i]][,1]) >> } >> >> #Something like??: (of course this doesn't work) >> savecol2=sapply(test, "[[", function(x) x[2,]) >> >> Thank you! >> >> Jeff >> >> ______________________________________________ >> R-help@stat.math.ethz.ch 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. > ______________________________________________ R-help@stat.math.ethz.ch 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.