Higher Memory consumption when compared to file size

[SinghB]

First of all, truly appreciate this package over xlsx package. I moved to this recently due to memory issues I was having. I'm not getting into memory errors but I do still see some large memory footprints. Hoping you can analyze this further or provide guidance on how the footprint can be reduced.
The data am writing in the sheets is about 1000 rows and 200 columns wide. I've 5-6 such sheets to be written. The final workbook size is ~4MB.

Here's the profiling output showcasing saveWorkbook and writeData memory usage, memout just contains my output from summaryRprof:

memout[which(grepl("book", noquote(rownames(memout) ))==TRUE),]
total.time total.pct mem.total self.time self.pct
"saveWorkbook" 22.08 9.98 451.7 0 0
"zipWorkbook" 1.38 0.62 0.1 0 0
"loadWorkbook" 0.88 0.40 11.4 0 0

Note the 451MB mem.total for saveWorkbook.

Also for writeData, the following is seen. Note that writeTS is a function of mine that internally calls writeData and saveWorkbook. Also, writeData only writes a sheet at a time and my workbook has multiple sheets, so total workbook size is ~4MB but each sheet should be still smaller.

memout[which(grepl("write", noquote(rownames(memout) ))==TRUE),]
total.time total.pct mem.total self.time self.pct
"writeTS" 52.52 23.75 893.8 0.44 0.20
"writeData" 13.98 6.32 210.1 0.00 0.00
"writeLines" 0.18 0.08 0.0 0.02 0.01

[awalker89]

which version of openxlsx are you using?

[SinghB]

The one on CRAN 3.0.1

[awalker89]

This is improved in the dev version.