It's because your first example produces answers of varying length so there's no natural way to coerce it to a matrix. Your second has a consistent length so the result can be made into a matrix.
Michael On Thu, Dec 8, 2011 at 4:30 PM, Doran, Harold <hdo...@air.org> wrote: > Suppose I have the following matrix > >> class(cov_50) > [1] "matrix" >> cov_50 > [,1] [,2] > [1,] 0.3201992 2.308084 > [2,] 6.7312928 5.719641 > > I then use the following function via apply and get the desired output, a list > > signif <- function(x) which(abs(x) > 1.96) > apply(cov_50, 1, signif) > >> apply(cov_50, 1, signif) > [[1]] > [1] 2 > > [[2]] > [1] 1 2 > > However, I can't see why the following occurs > >> class(cov_25) > [1] "matrix" >> cov_25 > [,1] [,2] > [1,] 12.116106 14.81248 > [2,] 5.492176 4.73138 > >> apply(cov_25, 1, signif) > [,1] [,2] > [1,] 1 1 > [2,] 2 2 > > So, using the same function (signif) on a different object of the same class > yields a matrix and *not* a list as desired. > > I can't see any reason for the different output. > >> sessionInfo() > R version 2.12.2 (2011-02-25) > Platform: x86_64-pc-mingw32/x64 (64-bit) > > locale: > [1] LC_COLLATE=English_United States.1252 LC_CTYPE=English_United States.1252 > [3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C > [5] LC_TIME=English_United States.1252 > > attached base packages: > [1] stats graphics grDevices utils datasets methods base > > other attached packages: > [1] quantreg_4.57 SparseM_0.86 > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. ______________________________________________ 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.
