Working with PRTools is subject to a set of global variables that control the operation of various routines. Here some information on the commands that control them is presented
If datasets become too large and hardly fit into the available memory, Matlab may crash or slows down due to heavy disk swapping. To prevent this the command
prmemory sets the maximum size of datasets. For larger sizes commands start to handle data, where possible, by an internal buffering procedure. Otherwise, an error is generated. The default value is
50*10^6 (in Matlab 8 byte doubles). Depending on the available hardware users may increase this.
An additional buffering scheme can be controlled by
setbatch. It controls the processing of datasets by mappings in batches.
Various routines depend on iterative optimization procedures. They stop when a particular accuracy has been reached or after a predetermined number of iterations. For some problems this might last prohibitively long. For that reason an additional condition has been included: such loops will stop after a globally set time. This guarantees a normal ending of all functions applied to any dataset, at the cost possibly sub-optimal results.
The routine that this controls is
prtime. It sets the maximum time in seconds allowed for a single iterative loop. By default this is 10 seconds. Users can change this number from the command line. A warning is generated each time a loop is prematurely ended by this routine.
PRTools has it own warning system to inform the user of unexpected situations or choices made in the software. It has four levels:
- 0: no warnings. The warning system is switched off.
- 1: show sever warnings only. These are useful for users as results might be wrong or need a different interpretation than might be expected.
- 2: show also warnings for the designer, e.g. when other procedures had to be used than demanded, e.g. due sample size problems or limited computer time.
- 3: show also light warnings, primarily useful for programmers.
Many PRTools routines estimate their progress and report this in a specific PRTools waitbar. This waitbar can be positioned by the user at an arbitrary location on the screen. The waitbar usually properly restarts after an error, except in case a command is stopped by Control-C. In that case the waitbar window should be deleted.
The waitbar overhead can be considerably, e.g. 20%. However, information about progress is often preferred over speed. In case of batch processing progress can be reported in the command window instead of graphically. Users can control the waitbar by the command
prwaitbar. Some useful options are
prwaitbar off: switch off the waitbar
prwaitbar on: switch on the waitbar
prwaitbar report: report progress not graphically but in the command window.
prwaitbar:reset the waitbar
plotc command that shows classifiers in a 2D feature space classify an NxN sampling of a region that is defined by a previous scatterplot (
scattern). By default N = 30. For complicated classifiers this is not sufficient. N = 100 or even N = 300 may be needed at the cost of a considerably larger computing time. Users can define N by the
User can inspect and reset global variables defined in PRTools by