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[英]R - How to change values in one Matrix based on elements in another Matrix
[英]How to change elements in one matrix indexed in another matrix?
我有兩個矩陣A和B.矩陣B是一個雙列矩陣,每行包含一個矩陣A中元素的索引。我想改變矩陣A中的那些元素,它們由矩陣B中的每一行索引,到0。
有沒有辦法避免使用下面顯示的循環?
> A <- matrix(1:12, 3, 4)
> B <- matrix(c(1, 2, 2, 2, 3, 4), byrow = TRUE, ncol = 2)
> A
[,1] [,2] [,3] [,4]
[1,] 1 4 7 10
[2,] 2 5 8 11
[3,] 3 6 9 12
> B
[,1] [,2]
[1,] 1 2
[2,] 2 2
[3,] 3 4
> for (i in 1:nrow(B)) {
+ A[B[i, 1], B[i, 2]] <- 0
+ }
> A
[,1] [,2] [,3] [,4]
[1,] 1 0 7 10
[2,] 2 0 8 11
[3,] 3 6 9 0
就是這樣做的
A[B] <- 0;
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