r - Cleaner way of constructing binary matrix from vector

Question

I have a fun challenge: I'm trying to construct a a binary matrix from an integer vector. The binary matrix should contain as many rows as the length of vector, and as many columns as the max value in the integer vector. The ith row in the matrix will correspond to the ith element of the vector, with the row containing a 1 at the position j, where j is equal to the value of the ith element of the vector; otherwise, the row contains zeros. If the value of the ith integer is 0, then the whole ith row should be 0.

To make this a whole lot simpler, here is a working reproducible example:

set.seed(1)
playv<-sample(0:5,20,replace=TRUE)#sample integer vector

playmat<-matrix(playv,nrow=length(playv),ncol=max(playv))#create matrix from vector

for (i in 1:length(playv)){
pos<-as.integer(playmat[i,1])
playmat[i,pos]<-1
playmat[i,-pos]<-0}

    head(playmat)
     [,1] [,2] [,3] [,4] [,5]
[1,]    1    0    0    0    0
[2,]    0    1    0    0    0
[3,]    0    0    1    0    0
[4,]    0    0    0    0    1
[5,]    1    0    0    0    0
[6,]    0    0    0    0    1

The above solution is correct, I'm just looking to make something more robust.

Answer 1

set.seed(1)
playv <- sample(0:5,20,replace=TRUE)
playv <- as.character(playv)
results <- model.matrix(~playv-1)

The columns in result you may rename.

I like the solution provided by Ananda Mahto and compared it to model.matrix. Here is a code

library(microbenchmark)

set.seed(1)
v <- sample(1:10,1e6,replace=TRUE)

f1 <- function(vec) {
  vec <- as.character(vec)
  model.matrix(~vec-1)
}

f2 <- function(vec) {
  table(sequence(length(vec)), vec)
}

microbenchmark(f1(v), f2(v), times=10)

model.matrix was a little bit faster then table

Unit: seconds
  expr      min       lq   median       uq      max neval
 f1(v) 2.890084 3.147535 3.296186 3.377536 3.667843    10
 f2(v) 4.824832 5.625541 5.757534 5.918329 5.966332    10