Sum each element of a vector with each element of a second vector

Question

I have two vectors and I want a matrix which elements are the sum of each element of vector 1 and each element of vector 2.

For example, the first element in the firs

Answer 1

This is how you would do it (note the matrix subset is not two brackets, but comma separated):

u <- c(1,2,3)
v <- c(4,5,6)

A <- matrix( c(1:6), 3, 3 )

for(i in 1:3)
{
   for(j in 1:3)
   {
      A[i,j] <- u[i]+v[j]
   }
}

But this is not the way someone who knows R would approach it. In general there are better ways to do things in R than nested for-loops. Another way is:

A <- outer(u,v,`+`)

Answer 2

We can also use sapply

sapply(u, `+`, v)