从n x m矩阵转换为R中的长矩阵 [英] Convert from n x m matrix to long matrix in R

问题描述

注意:这不是图形问题.

Note: This is not a graph question.

我有一个n x m的矩阵:

I have an n x m matrix:

> m = matrix(1:6,2,3)
> m
  a  b  c
d 1  2  3
e 4  5  6

我想将其转换为长矩阵:

I would like to convert this to a long matrix:

> m.l
a d 1
a e 4
b d 2
b e 5
c d 3
c e 6

显然嵌套循环是可行的，但是我知道有很多不错的工具可以用于重塑R中的矩阵.到目前为止，我只发现了有关将长矩阵或宽矩阵转换为nxm矩阵的文献，而没有其他方法.我缺少明显的东西吗?我该如何进行转换?

Obviously nested for loops would work but I know there are a lot of nice tools for reshaping matrixes in R. So far, I have only found literature on converting from long or wide matrixes to an n x m matrix and not the other way around. Am I missing something obvious? How can I do this conversion?

谢谢！

推荐答案

如果您需要单个列矩阵

 matrix(m, dimnames=list(t(outer(colnames(m), rownames(m), FUN=paste)), NULL))
 #    [,1]
 #a d    1
 #a e    4
 #b d    2
 #b e    5
 #c d    3
 #c e    6

对于data.frame输出，可以使用reshape2

For a data.frame output, you can use melt from reshape2

 library(reshape2)
 melt(m)

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