合并具有相同列名的矩阵中的列 [英] Combine columns in matrix having same column name

问题描述

我有一个矩阵，其中的列重复字符列名称。

I have a matrix with columns that duplicate character column names.

set.seed(1)
m <- matrix(sample(1:10,12,replace=TRUE), nrow = 3, ncol = 4, byrow = TRUE,
       dimnames = list(c("s1", "s2", "s3"),c("x", "y","x","y")))

m
   x y  x  y
s1 3 4  6 10
s2 3 9 10  7
s3 7 1  3  2

我需要将具有相同列名的所有列加总为一个列，即

I need to sum all columns with the same column name into only one column i.e.

m <- matrix(c(9,14,13,16,10,3), nrow = 3, ncol = , byrow = TRUE,dimnames = list(c("s1", "s2", "s3"),c("x", "y")))

    x  y
s1  9 14
s2 13 16
s3 10  3

我在汇总函数中玩过简单的和，但是没有任何运气。有什么建议吗？谢谢。

I have had a play with the simple sum in the aggregate function but haven't had any luck. Any advice? Thanks.

推荐答案

好吧，此解决方案不会因代码透明性而获得任何奖项，但我更喜欢它：

Well, this solution won't win any awards for transparency of code, but I rather like it:

nms <- colnames(m)
m %*% sapply(unique(nms),"==", nms)
#     x  y
# s1  9 14
# s2 13 16
# s3 10  3

---

它的工作原理是构建一个矩阵，该矩阵形成 m 列的适当线性组合。若要查看其工作原理，请将第二行分成两个分量矩阵，使用％*％相乘，如下所示：

---

It works by constructing a matrix that forms appropriate linear combinations of m's columns. To see how it works, pick apart the second line into its two component matrices, which are multiplied together using %*%, like this:

 -          -      -   -
|  3 4  6 10 |    | 1 0 |
|  3 9 10  7 |    | 0 1 |
|  7 1  3  2 |    | 1 0 |
 -          -     | 0 1 |
                   -   -

这篇关于合并具有相同列名的矩阵中的列的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！