Turn objects into the sparseMatrix as defined in the Matrix package.
as.sparseMatrix(x, ...)# S4 method for simple_triplet_matrix
as.sparseMatrix(x, ...)
# S4 method for TermDocumentMatrix
as.sparseMatrix(x, ...)
# S4 method for bundle
as.sparseMatrix(x, col)
object to convert
further parameters
column name to get values from (if x is a bundle)