select some values of a row in a matrix

Question

In R with a matrix:

m <- matrix(1:20, ncol = 4) 
colnames(m) <- letters[1:4]

In the case I want to select just one value, it works. Like

Answer 1

Change == by %in%

subset(m, m[,4] %in% c(17,19,20))

Answer 2

without using subset

m[ m[,4] %in% c(17, 19, 20),]