user2806363 user2806363 - 1 year ago 43
R Question

given value of matrix, getting it's coordinate

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 Source

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
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