Return the proportion of sparseness of a document-feature matrix, equal
to the proportion of cells that have zero counts.
the document-feature matrix
inaug_dfm <- dfm
, verbose = FALSE
#>  0.9176184
, min_termfreq = 5
#> Error in .setupMethodsTables(fdef): trying to get slot "group" from an object of a basic class ("NULL") with no slots