R 中矩阵的索引值？

发布于 2024-08-13 07:20:32 字数 509 浏览 3 评论 0原文

是否有一个函数可以获取矩阵的索引（行号和列号）？

假设我有一个简单的矩阵：

a <- matrix(1:50, nrow=5)

例如，是否有一种简单的方法可以返回数字“23”的 c(3, 5) 之类的值？在这种情况下，说 which(a==23) 仅返回 23。

这似乎有效，但我确信有更好的方法：

matrix.index <- function(a, value) {
  idx <- which(data.frame(a)==value)
  col.num <- ceiling(idx/nrow(a))
  row.num <- idx - (col.num-1) * nrow(a)
  return(c(row.num, col.num))
}
> matrix.index(a, 23)
[1] 3 5
> matrix.index(a, 50)
[1]  5 10

原文

Is there a function to get an index (row number and column number) for a matrix?

Suppose that I have a simple matrix:

a <- matrix(1:50, nrow=5)

Is there an easy way to get back something like c(3, 5) for the number "23", for instance? In this case, saying which(a==23) just returns 23.

This seems to work but I'm sure that there's a better way:

matrix.index <- function(a, value) {
  idx <- which(data.frame(a)==value)
  col.num <- ceiling(idx/nrow(a))
  row.num <- idx - (col.num-1) * nrow(a)
  return(c(row.num, col.num))
}
> matrix.index(a, 23)
[1] 3 5
> matrix.index(a, 50)
[1]  5 10

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无边思念无边月 2024-08-20 07:20:32

发布此文章后，查看了 which() 的帮助，找到了答案：arr.ind 参数。

which(a==23, arr.ind=TRUE)
     row col
[1,]   3   5

Just looked at the help for which() after posting this and found the answer: the arr.ind parameter.

which(a==23, arr.ind=TRUE)
     row col
[1,]   3   5

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放手` 2024-08-20 07:20:32

m = matrix(c(1:16), nrow = 4, byrow = TRUE)
print("Original Matrix:")
print(m)
result = which(m == max(m), arr.ind=TRUE)
print("Row and column of maximum value of the said matrix:")
print(result)
result = which(m == min(m), arr.ind=TRUE)
print("Row and column of minimum value of the said matrix:")
print(result)

m = matrix(c(1:16), nrow = 4, byrow = TRUE)
print("Original Matrix:")
print(m)
result = which(m == max(m), arr.ind=TRUE)
print("Row and column of maximum value of the said matrix:")
print(result)
result = which(m == min(m), arr.ind=TRUE)
print("Row and column of minimum value of the said matrix:")
print(result)

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