How to construct a function call to pmax from the columns of a matrix

Question

I want to use pmax to compute the row-wise maximium of a matrix A:

A = matrix(sample(1:20),10,2)
pmax(A[,1],A[,2])

this works fine. But the problem is that I don't know the size of A, so the call to pmax should be able to split the matrix by columns and supply each column as an argument. how to do that? For example, I may in the next instance have

A = matrix(sample(1:20),5,4)

But I don't want to have to rewrite by hand every time to

pmax(A[,1],A[,2],A[,3],A[,4])

in fact, I can't because the size of A is unknown before the start of the program.

Answer 1

You can use do.call:

do.call(pmax, as.data.frame(A))

Answer 2

Just use apply with max instead...

apply( A , 1 , max )
# [1]  6 11 20 18 17

pmax(A[,1],A[,2],A[,3],A[,4])
# [1]  6 11 20 18 17