Thanks for your replies ! The lapply hack does the job in my context, so I'll stick to it (and actually in any case where I expect variable length results).
About your quote from ?apply : I read it some time ago actually - but with my recent use in "variable length returning FUN", I got fooled... On Fri, Mar 8, 2013 at 10:43 AM, Patrick Burns <[email protected]>wrote: > This is nice fodder for 'The R Inferno' -- thanks. > > As Milan said, 'which' will suffice as the function. > > Here is a specialized function that only returns a > list and is only implemented to work with matrices. > It should solve your current dilemma. > > applyL <- > function (X, MARGIN, FUN, ...) > { > stopifnot(length(dim(X)) == 2, length(MARGIN) == 1) > > FUN <- match.fun(FUN) > ans <- vector("list", dim(X)[MARGIN]) > if(MARGIN == 1) { > for(i in seq_along(ans)) { > ans[[i]] <- FUN(X[i,], ...) > } > } else { > for(i in seq_along(ans)) { > ans[[i]] <- FUN(X[,i], ...) > } > } > names(ans) <- dimnames(X)[[MARGIN]] > ans > } > > > Pat > > > > On 08/03/2013 08:29, Pierrick Bruneau wrote: > >> Hello everyone, >> >> Considering the following code sample : >> >> ---- >> indexes <- function(vec) { >> vec <- which(vec==TRUE) >> return(vec) >> } >> mat <- matrix(FALSE, nrow=10, ncol=10) >> mat[1,3] <- mat[3,1] <- TRUE >> ---- >> >> Issuing apply(mat, 1, indexes) returns a 10-cell list, as expected. >> Now if I do: >> >> ---- >> mat[1,3] <- mat[3,1] <- FALSE >> apply(mat, 1, indexes) >> ---- >> >> I would expect a 10-cell list with integer(0) in each cell - instead I get >> integer(0), which wrecks my further process. >> Is there a simple way to get the result I expect (and the only consistent >> one, IMHO) ? >> >> Thanks by advance for your help, >> >> Pierrick Bruneau >> http://www.bruneau44.com >> >> [[alternative HTML version deleted]] >> >> ______________________________**________________ >> [email protected] mailing list >> https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help> >> PLEASE do read the posting guide http://www.R-project.org/** >> posting-guide.html <http://www.R-project.org/posting-guide.html> >> and provide commented, minimal, self-contained, reproducible code. >> >> > -- > Patrick Burns > [email protected] > twitter: @burnsstat @portfolioprobe > http://www.portfolioprobe.com/**blog <http://www.portfolioprobe.com/blog> > http://www.burns-stat.com > (home of: > 'Impatient R' > 'The R Inferno' > 'Tao Te Programming') > [[alternative HTML version deleted]] ______________________________________________ [email protected] 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.
