21.21 Conversion to Matrix and Save to CSV

We can convert the document term matrix to a simple matrix for writing to a CSV file, for example, for loading the data into other software if we need to do so. To write to CSV we first convert the data structure into a simple matrix:

m <- as.matrix(dtm)
dim(m)

## [1]   46 6508

For very large corpus the size of the matrix can exceed R’s calculation limits. This will manifest itself as a integer overflow error with a message like:

## Error in vector(typeof(x$v), nr * nc) : vector size cannot be NA
## In addition: Warning message:
## In nr * nc : NAs produced by integer overflow

If this occurs, then consider removing sparse terms from the document term matrix, as we discuss shortly.

Once converted into a standard matrix the usual utils::write.csv() can be used to write the data to file.

write.csv(m, file="dtm.csv")

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