Fast way to create a binary matrix with known number of 1 each row in R

Question

I have a vector that provides how many \"1\" each row of a matrix has. Now I have to create this matrix out of the vector.

For example, let say I want to create a 4 x 9

Answer 1

One option is sparseMatrix from Matrix

library(Matrix)
m1 <- sparseMatrix(i = rep(seq_along(v), v), j = sequence(v), x = 1)
m1
#4 x 9 sparse Matrix of class "dgCMatrix"

#[1,] 1 1 . . . . . . .
#[2,] 1 1 1 1 1 1 . . .
#[3,] 1 1 1 . . . . . .
#[4,] 1 1 1 1 1 1 1 1 1

This can be converted to matrix with as.matrix

as.matrix(m1)