Question

I have a sparse matrix (dgCMatrix) as the result of fitting a glmnet. I want to write this result to a .csv but can’t use write.table() the matrix because it can’t coerced into a data.frame.

Is there a way to coerce the sparse matrix to either a data.frame or a regular matrix? Or is there a way to write it to a file while keeping the coefficient names which are probably row names?

Answer 1

as.matrix() will convert to the full dense representation:

> as.matrix(Matrix(0, 3, 2))
     [,1] [,2]
[1,]    0    0
[2,]    0    0
[3,]    0    0

You can write the resulting object out using write.csv or write.table.