Write a gzip compressed Matrix Market file in R.

writeMMgz.R

#' @param x A sparse matrix from the Matrix package.
#' @param file A filename that ends in ".gz".
writeMMgz <- function(x, file) {
  mtype <- "real"
  if (is(x, "ngCMatrix")) {
    mtype <- "integer"
  }
  writeLines(
    c(
      sprintf("%%%%MatrixMarket matrix coordinate %s general", mtype),
      sprintf("%s %s %s", x@Dim[1], x@Dim[2], length(x@x))
    ),
    gzfile(file)
  )
  data.table::fwrite(
    x = summary(x),
    file = file,
    append = TRUE,
    sep = " ",
    row.names = FALSE,
    col.names = FALSE
  )
}