list - R: Index matrix row-wise in vectors -


i have vector containing character elements, say

v <- c("a","b","c")

and matrix containing logical elements, width equal length of v , arbitrary length:

> m <- matrix(c(true,false,true,false,true,true),ncol=3,byrow=true) > m       [,1]  [,2] [,3] [1,]  true false true [2,] false  true true

now index each row of m v, collapse, , obtain vector r each element of contains corresponding row of m in 1 character expression. in example given, elements of r 

> r "a c" "b c"

i can each row separately (or within loop), using 

r[i] <- paste(v[as.logical(m[i,])], collapse="")

but hoped there more efficient solution deals full matrix @ once.

we can use apply margin=1

apply(m, 1, function(x) paste(v[x], collapse=' ')) #[1] "a c" "b c"

data

 m <- matrix(c(true,false,true,false,true,true),ncol=3, byrow=true)

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