Set on package load to a "plotfiles" subdirectory of
tempdir(). Used by the rApache handlers plotter
and plotterpro as the destination directory for generated
PDF, PNG, CSV and TXT files, and by upload_tryCatch_pro as
the destination for uploaded data files and the .RData file it
hands off to plotterpro. The directory itself is only created
lazily, on the first actual write inside these handlers – not merely by
loading the package – so calling library(tanner) to use unrelated
functions like calculate_sds has no disk side effects.
Reassign this before calling the handlers to change where they read/write.