Matrix representation of categories in R

Question

I have a column with a set of categories e.g. Category1, Category2, Category3,Category2, etc. Is there any way to represent them in R as a matrix with the following view:

Category1 Category2 Category3
        1         0         0
        0         1         0
        0         0         1
        0         1         0
        ...       ...       ...

Any feedback is greatly appreciated.

Answer 1

I would do the following:

matrixForm <- function(X) {
   values <- sort(unique(X))
   outM <- matrix(0, nrow=length(X), ncol=length(values))
   for (i in 1:ncol(outM)) outM[,i] <- as.numeric(X==values[i])
   colnames(outM) <- values
   return(outM)
}

X is an input vector of characters. So the result...

X <- c('Category1','Category2','Category2','Category3','Category1','Category3')
matrixForm(X)
#################
     Category1 Category2 Category3
[1,]         1         0         0
[2,]         0         1         0
[3,]         0         1         0
[4,]         0         0         1
[5,]         1         0         0
[6,]         0         0         1