Returns the location of the supplementary results directory.
The supplementary results directory provides a place to store
results in addition to the results saved by the psychTestR
function save_results_to_disk
.
The researcher has full control over what to put in the supplementary
results directory.
get_supplementary_results_dir(opt)
Options list as created by test_options()
.
Character scalar identifying the (relative) path to the supplementary results directory.
The supplementary results directory is typically stored within the main results directory. It will be deleted if the researcher presses the 'Delete all results' button in the admin panel.