R中的嵌套双循环

Question

mat <- matrix(0,ncol=6, nrow=100)
d=c(1,2,4,8,16,32)
for(i in 1:6)
{
  for(j in d)
  {
    mat[,i]=rep(j,100)
  }
}
mat

I should get a 100 x 6 matrix with columns of 1,2,4,8,16,32. However, I simply get rows of 32 in every column. Does anyone have any idea how I can fix this. I do want to use loops, even if its one loop that's fine.

Answer 1

Based on your description: 100 rows x 6 columns, column 1 = value 1...column 6 = value 32, this should generate what you want.

matrix(data = rep(c(1,2,4,8,16,32), each = 100), 
       nrow = 100, 
       ncol = 6)

Answer 2

The answer from @neilfws is more elegant. If you are committed to using a loop for some reason you can do this

mat <- matrix(0,ncol=6, nrow=100)
d=c(1,2,4,8,16,32)
for(i in 1:6)
{
  j <- d[i]

    mat[,i]=rep(j,100)

}
mat

The issue is that you were looping through all of d for each column.