I am trying to run the tutorial for written exams in the exams package (http://www.r-exams.org/tutorials/exams2nops/). Everything works fine until I am about to process the scanned documents using the nops_scan function, which normally should create a zip file.
In the console it says "Creating ZIP file", but nothing happens after that. Last output:
> nops_scan(dir = "nops_scan")
Loading required namespace: png
Reading PNG files:nops_scan1.png: Trimming PNG, rotating PNG,
extracting information, done.nops_scan2.png: Trimming PNG, rotating
PNG, extracting information, done.
Creating ZIP file:
... and then nothing happens.
I have tried to run dir("nops_scan") and it confirms that no zip file has been generated and placed in this folder.
The files in the tutorial are png-files, so what the tutorials says about running pdftk and ImageMagick, should not apply. From the tutorial: "Note that if there were PDF files that need to be scanned, then the PDF toolkit pdftk and the function convert from ImageMagick need to be available outside of R on the command line."
Could the problem still be related to the above comment about pdftk or ImageMagick? (Which program is used to create the zip files?) I do not know how to make these programs "available outside of R", so instruction on this would be appreciated!
The base zip() function from the tools package is used, see ?zip. If you are on Windows maybe you need to install the Rtools? These are available from CRAN at https://CRAN.R-project.org/bin/windows/Rtools/.
PDFTk and ImageMagick are not involved in this case, they are only needed to convert PDF files to PNG which can then be processed in R. (And just in case anybody else is looking for this information: http://www.R-exams.org/tutorials/installation/ provides links to installation files for these applications.)