I hope someone experience with plyr package comes and helps because this
sounds like what it does well, but for your specific example something like
this works:
A = rbind(a,a2)
q = apply(A,2,function(x) {lm(x[1:nrow(a)] ~ x[-(1:nrow(a))])})
but yeah, that's pretty rough so I hope someone can come up with something
more elegant.
If nothing else, I think that idea can be made to work in most
circumstances: put it together, then break it apart inside the function
passed to apply.
Michael Weylandt
On Thu, Aug 4, 2011 at 5:17 PM, Jim Bouldin <[email protected]> wrote:
> 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]]
>
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> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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