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.