create a sparse matrix; given the indices of non-zero elements for creation of dummy variables of a categorical column of a large dataset

Question

I\'m trying to use a sparse matrix to generate dummy variables for a set of data with 5.8 million rows and two categorical columns.

The structure of the data is:

Answer 1

Try this:

spmat<-Matrix(0,nrow = 210000 ,ncol = 500,sparse = T)
locs<-Matrix(data=c(mydata$Var_1,mydata$Var_2),byrow=F,ncol=2)
spmat[locs]=1