Matrix multiplication by specific amount

Question

I need to create matrix 100x100 and multiply by 2 every record bigger then 5000 and I'm giving up :/

Code for matrix

m <- matrix(1:10000, nrow = 100, ncol = 100)

Can somebody help me ?

Don't understand "multiply by 2 every record bigger then 5000"... can you show what do you mean? — ThomasIsCoding, Jan 15 '20 at 19:12
It's easier to help you if you include a simple [reproducible example](https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example) with sample input and desired output that can be used to test and verify possible solutions. — MrFlick, Jan 15 '20 at 19:12

score 2 · Accepted Answer · answered Jan 15 '20 at 19:19

2

I think this code solve your problem:

m[m > 5000] = 2*m[m>5000]

Also:

m = ifelse(m > 5000, 2*m, m)

answered Jan 15 '20 at 19:19

Filipe Lauar

Thank you so much, bro! – Adrian Stodolski Jan 15 '20 at 19:32
To keep the `dim` attribute you must do `m[] = ifelse(etc)`. Upvote for the first code line. – Rui Barradas Jan 15 '20 at 19:36

score 0 · Answer 2 · answered Jan 15 '20 at 19:18

0

n <- apply(m, 2, function(x) ifelse(x > 5000, x*2, x))

answered Jan 15 '20 at 19:18

Ane

2 Answers2