r - Functional way to stack list of 2d matrices into 3d matrix -


after clever lapply, i'm left list of 2-dimensional matrices.

for example:

set.seed(1) test <- replicate( 5,  matrix(runif(25),ncol=5), simplify=false ) > test [[1]]           [,1]       [,2]      [,3]      [,4]      [,5] [1,] 0.8357088 0.29589546 0.9994045 0.2862853 0.6973738 [2,] 0.2377494 0.14704832 0.0348748 0.7377974 0.6414624 [3,] 0.3539861 0.70399206 0.3383913 0.8340543 0.6439229 [4,] 0.8568854 0.10380669 0.9150638 0.3142708 0.9778534 [5,] 0.8537634 0.03372777 0.6172353 0.4925665 0.4147353  [[2]]           [,1]      [,2]      [,3]      [,4]      [,5] [1,] 0.1194048 0.9833502 0.9674695 0.6687715 0.1928159 [2,] 0.5260297 0.3883191 0.5150718 0.4189159 0.8967387 [3,] 0.2250734 0.2292448 0.1630703 0.3233450 0.3081196 [4,] 0.4864118 0.6232975 0.6219023 0.8352553 0.3633005 [5,] 0.3702148 0.1365402 0.9859542 0.1438170 0.7839465  [[3]] ...

i'd turn 3-dimensional array:

set.seed(1) replicate( 5,  matrix(runif(25),ncol=5) )

obviously, if i'm using replicate can turn on simplify, sapply not simplify result properly, , stack fails utterly. do.call(rbind,mylist) turns 2d matrix rather 3d array.

i can loop, i'm looking neat , functional way handle it.

the closest way i've come is:

array( do.call( c, test ), dim=c(dim(test[[1]]),length(test)) )

but feel that's inelegant (because disassembles , reassembles array attributes of vectors, , needs lot of testing make safe (e.g. dimensions of each element same).

you can use abind package , use do.call(abind, c(test, along = 3))

library(abind) testarray <- do.call(abind, c(test, along = 3))

or use simplify = 'array' in call sapply, (instead of lapply). simplify = 'array' not same simplify = true, change argument higher in simplify2array

eg

foo <- function(x) matrix(1:10, ncol = 5) # default simplify = true sapply(1:5, foo)       [,1] [,2] [,3] [,4] [,5]  [1,]    1    1    1    1    1  [2,]    2    2    2    2    2  [3,]    3    3    3    3    3  [4,]    4    4    4    4    4  [5,]    5    5    5    5    5  [6,]    6    6    6    6    6  [7,]    7    7    7    7    7  [8,]    8    8    8    8    8  [9,]    9    9    9    9    9 [10,]   10   10   10   10   10 # *not* want # set `simplify = 'array' sapply(1:5, foo, simplify = 'array') , , 1       [,1] [,2] [,3] [,4] [,5] [1,]    1    3    5    7    9 [2,]    2    4    6    8   10  , , 2       [,1] [,2] [,3] [,4] [,5] [1,]    1    3    5    7    9 [2,]    2    4    6    8   10  , , 3       [,1] [,2] [,3] [,4] [,5] [1,]    1    3    5    7    9 [2,]    2    4    6    8   10  , , 4       [,1] [,2] [,3] [,4] [,5] [1,]    1    3    5    7    9 [2,]    2    4    6    8   10  , , 5       [,1] [,2] [,3] [,4] [,5] [1,]    1    3    5    7    9 [2,]    2    4    6    8   10

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