On Fri, 2005-08-26 at 15:25 +0200, Peter Dalgaard wrote: > Marc Schwartz <[EMAIL PROTECTED]> writes: > > > x <- c(0.005, 0.010, 0.025, 0.05, 0.1, 0.5, 0.9, > > 0.95, 0.975, 0.99, 0.995) > > > > df <- c(1:100) > > > > mat <- sapply(x, qchisq, df) > > > > > dim(mat) > > [1] 100 11 > > > > > str(mat) > > num [1:100, 1:11] 3.93e-05 1.00e-02 7.17e-02 2.07e-01 4.12e-01 ... > > outer() is perhaps a more natural first try... It does give the > transpose of the sapply approach, though. > > round(t(outer(x,df,qchisq)),2) > > should be close. You should likely add dimnames.
What I find interesting, is that I would have intuitively expected outer() to be faster than sapply(). However: > system.time(mat <- sapply(x, qchisq, df), gcFirst = TRUE) [1] 0.01 0.00 0.01 0.00 0.00 > system.time(mat1 <- round(t(outer(x, df, qchisq)), 2), gcFirst = TRUE) [1] 0.01 0.00 0.01 0.00 0.00 # No round() or t() to test for overhead > system.time(mat2 <- outer(x, df, qchisq), gcFirst = TRUE) [1] 0.01 0.00 0.02 0.00 0.00 # Bear in mind the round() on mat1 above > all.equal(mat, mat1) [1] "Mean relative difference: 4.905485e-05" > all.equal(mat, t(mat2)) [1] TRUE Even when increasing the size of 'df' to 1:1000: > system.time(mat <- sapply(x, qchisq, df), gcFirst = TRUE) [1] 0.16 0.01 0.16 0.00 0.00 > system.time(mat1 <- round(t(outer(x, df, qchisq)), 2), gcFirst = TRUE) [1] 0.16 0.00 0.18 0.00 0.00 > # No round() or t() to test for overhead > system.time(mat2 <- outer(x, df, qchisq), gcFirst = TRUE) [1] 0.16 0.01 0.17 0.00 0.00 It also seems that, at least in this case, t() and round() do not add much overhead. Best regards, Marc ______________________________________________ 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