I realize this should be simple, but even after reading over the several help pages several times, I still cannot decide between the myriad "apply" functions to address it. I simply want to apply a function to all the rows (or columns) of the same index from two (or more) identically sized arrays (or data frames).
For example: > a=matrix(1:50,nrow=10) > a2=floor(jitter(a,amount=50)) > a [,1] [,2] [,3] [,4] [,5] [1,] 1 11 21 31 41 [2,] 2 12 22 32 42 [3,] 3 13 23 33 43 [4,] 4 14 24 34 44 [5,] 5 15 25 35 45 [6,] 6 16 26 36 46 [7,] 7 17 27 37 47 [8,] 8 18 28 38 48 [9,] 9 19 29 39 49 [10,] 10 20 30 40 50 > a2 [,1] [,2] [,3] [,4] [,5] [1,] 31 56 -29 -13 10 [2,] 38 61 71 55 9 [3,] -29 38 47 12 38 [4,] 12 2 43 39 93 [5,] -43 23 -23 62 1 [6,] -13 61 55 11 2 [7,] -42 1 38 12 8 [8,] -13 -6 -18 16 95 [9,] -19 -2 78 33 1 [10,] 20 -16 -11 19 17 if I try the following for example: apply(a,1,function(x) lm(a~a2)) I get 10 identical repeats (except for the list indexer) of the following: [[1]] Call: lm(formula = a ~ a2) Coefficients: [,1] [,2] [,3] [,4] [,5] (Intercept) 8.372135 18.372135 28.372135 38.372135 48.372135 a21 -0.006163 -0.006163 -0.006163 -0.006163 -0.006163 a22 -0.093390 -0.093390 -0.093390 -0.093390 -0.093390 a23 0.009315 0.009315 0.009315 0.009315 0.009315 a24 -0.015143 -0.015143 -0.015143 -0.015143 -0.015143 a25 -0.026761 -0.026761 -0.026761 -0.026761 -0.026761 ...Which is clearly very wrong, in a number of ways. If I try by columns: apply(a,2,function(x) lm(a~a2)) ...I get exactly the same result. So, which is the appropriate apply-type function when two arrays (or d.f.'s?) are involved like this? Or none of them and some other approach (other than looping which I can do but which I assume is not optimal)? Thanks for any help. -- Jim Bouldin, PhD Research Ecologist [[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.