[R] How to join matrices of different row length from a list
Gabor Grothendieck
ggrothendieck at gmail.com
Thu Jan 6 17:10:37 CET 2011
On Thu, Jan 6, 2011 at 5:56 AM, emj83 <stp08emj at shef.ac.uk> wrote:
>
> Hi,
>
> I have several matrix in a list, for example:
> e
> [[1]]
> [,1] [,2]
> [1,] 1 3
> [2,] 2 4
>
> [[2]]
> [,1] [,2]
> [1,] 1 4
> [2,] 2 5
> [3,] 3 6
>
> [[3]]
> [,1] [,2]
> [1,] 2 1
>
> I would like to join them by column i.e.
> [,1] [,2] [,3] [,4][,5] [,6]
> [1,] 1 3 1 4 2 1
> [2,] 2 4 2 5 NA NA
> [3,] NA NA 3 6 NA NA
>
> I have tried do.call(cbind,e) but I get this error message as the rows are
> of different length-
> Error in function (..., deparse.level = 1) :
> number of rows of matrices must match (see arg 2)
>
One reasonably simple approach is to convert your matrices to time
series (either ts series or zoo series) as cbind.ts and cbind.zoo both
NA fill.
L <- list(matrix(1:4, 2, 2), matrix(1:6, 3, 2), matrix(2:1, 1, 2))
# using ts
M <- unclass(do.call(cbind, lapply(L, ts)))
tsp(M) <- colnames(M) <- NULL
# With zoo its slightly shorter:
library(zoo)
M <- coredata(do.call(cbind, lapply(L, zoo)))
colnames(M) <- NULL
We can omit the colnames(M) <- NULL part in both cases if the list
itself or the constituent matrices have column names, e.g.
L <- list(A = matrix(1:4, 2, 2), B = matrix(1:6, 3, 2), C = matrix(2:1, 1, 2))
# or
L <- list(cbind(a = 1:2, b = 3:4), cbind(c = 1:3, d = 4:6), cbind(e = 2, f = 1))
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