交错存储在R中的列表中的矩阵行 [英] interleave rows of matrix stored in a list in R

问题描述

我想从矩阵列表中创建交错矩阵.

I want to create interleaved matrix from a list of matrices.

示例输入:

> l <- list(a=matrix(1:4,2),b=matrix(5:8,2))
> l
$a
     [,1] [,2]
[1,]    1    3
[2,]    2    4

$b
     [,1] [,2]
[1,]    5    7
[2,]    6    8

预期输出:

1    3
5    7
2    4
6    8

我已经检查了gdata中的interleave函数，但是它没有显示列表的这种行为.任何帮助表示赞赏.

I have checked the interleave function in gdata but it does not show this behaviour for lists. Any help appreciated.

推荐答案

这里是单线:

do.call(rbind, l)[order(sequence(sapply(l, nrow))), ]
#      [,1] [,2]
# [1,]    1    3
# [2,]    5    7
# [3,]    2    4
# [4,]    6    8

为帮助理解，首先将矩阵与do.call(rbind, l)堆叠在一起，然后以正确的顺序提取行:

To help understand, the matrices are first stacked on top of each other with do.call(rbind, l), then the rows are extracted in the right order:

sequence(sapply(l, nrow))
# a1 a2 b1 b2 
#  1  2  1  2 

order(sequence(sapply(l, nrow)))
# [1] 1 3 2 4

它将适用于任意数量的矩阵，并且即使行数不相同，它也会做正确的事情"(主观).

It will work with any number of matrices and it will do "the right thing" (subjective) even if they don't have the same number of rows.

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