given value of matrix, getting it's coordinate

Question

I have matrix, I want to write a function, get the element of matrix and return me the coordinate of number inside of matrix. could somebody give an idea how to implement it ?

> A
     [,1] [,2]
[1,]   10   20
[2,]   21   17
[3,]   13   25
[4,]   21   11
[5,]   31   24

for example

myfunction(11)

> 11
> row 3, col 1

Answer 1

which() takes an argument, arr.ind=TRUE, which will return the indices of all TRUE elements in a logical matrix to which it is applied.

## An example matrix
set.seed(1)
m <- matrix(sample(1:100, 10), ncol=2)
m
#      [,1] [,2]
# [1,]   27   86
# [2,]   37   97
# [3,]   57   62
# [4,]   89   58
# [5,]   20    6

## An example application 
which(m==58, arr.ind=TRUE)
#      row col
# [1,]   4   2