Edward Armstrong - 1 year ago 63

R Question

If I have a matrix:

`mat=matrix(c(-21,14,28,17,-16,-9,-17,-30,18), nrow=3)`

mat

[,1] [,2] [,3]

[1,] -21 17 17

[2,] 14 -16 -30

[3,] 28 -9 18

I can isolate the highest absolute value simply with

`max(abs(mat))`

However how do I preserve the sign so I return -30?

For some context, I have a large number of matrices and I need a command to isolate the highest absolute number in all of them including the sign (some will be positive others negative).

Thanks in advance!

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Answer Source

You need the index of the value in the matrix which is the maximum absolute value, which you can then use to return the value itself. `which.max`

will do this (and `which.min`

for the opposite):

```
mat[which.max( abs(mat) )]
# [1] -30
```

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