将2d矩阵列表堆叠成3d矩阵的功能方法

Question

聪明之后lapply,我留下了一个二维矩阵列表.

例如:

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]]
...

我想把它变成一个三维数组:

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

显然,如果我使用复制,我可以打开simplify,但sapply不能正确简化结果,并stack完全失败. do.call(rbind,mylist)把它变成2d矩阵而不是3d数组.

我可以用循环来做到这一点,但我正在寻找一种简洁实用的方法来处理它.

我提出的最接近的方式是:

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

但我觉得它不够优雅(因为它反汇编然后重新组装向量的数组属性,并且需要大量测试才能确保安全(例如每个元素的尺寸相同).

Answer 1

试试这个:

simplify2array(test)

Answer 2

您可以使用该abind包然后使用abind(test, along = 3)

library(abind)
testArray <- abind(test, along = 3)

或者您可以simplify = 'array'在呼叫中使用sapply,(而不是lapply).simplify = 'array'是不一样的simplify = TRUE,因为它会改变说法higher在simplify2array

例如

foo <- function(x) matrix(1:10, ncol = 5)
# the default is 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
# which is *not* what you want
# so 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