ManualAdvancedCreatingCustomFunctions

Advanced Manual

Creating custom functions

It is very easy to override the toolbox's default functions with your own custom-created function that the main toolbox control functions can call when appropriate. For instance, if you don't want to use the default backpropagation classifier, or the default ANOVA statmap generator, you can drop your own functions in instead, and the toolbox's no-peeking cross-validation control functions will use your custom functions instead at the appropriate times.

At the moment, there are various places where you can substitute your own functions ' click on the links in the list below to skip to the section where the specific details for each are described.

If you do create a custom function and you think others might benefit from it, we'd really like to hear from you so that we can incorporate it into future releases of the toolbox.

Places that can call custom function

• statmap generation ' feature_selection.m and peek_feature_selection.m can take optional statmap_funct and statmap_arg arguments
• classifier training ' cross_validation.m can take an optional train_funct function name string
• classifier test ' cross_validation.m can take an optional test_funct function name string
• classifier performance metrics ' cross_validation.m can take an optional perfmet_functs cell array of performance metric function name strings

Requirements for custom functions that modify the subj structure

Any custom functions that modify the subj structure (usually by creating a new object) should fulfil the following requirements, if they're going to be well-behaved toolbox citizens:

· take in a subj structure as their first argument

· return the modified subj structure as their first output argument

· if the custom function creates a new subj structure object, you should add a line to the help comments that says 'Adds the following objects:' and a list of the objects/groups that get created

· if the custom function creates a new subj structure object, you should display something like:

sprintf('Created %s called %s',objtype,objname)

• should call the add_created.m with fields for the name of the function and any arguments it takes
• should call add_history.m to add a line describing themselves to their own freetext history narrative
• try and do some error-checking on the inputs, if there are any assumptions that the function makes, to help future users avoid making hard-to-debug booboos