Error when running a script: 'Index exceeds matrix dimensions.' Help

I've been given a script to run to merge EEG and psychophysics test files and am having some difficulty running it. Part of the way through the script a new variable ('MatchedEEG') is created from an existing matrix, containing all EEG traces up until a given time point (Endidx):

MatchedEEG = EEGtraces (:,1:Endidx)

I receive an error saying: 'Index exceeds matrix dimensions.' How can the index exceed the matrix dimensions if no pre-determined matrix dimensions are specified for 'MatchedEEG'? Help.

Answer 1

[Adam]

The index 'Endidx' presumably exceeds the size of the 2nd dimension of EEGtraces. It is indexing into that matrix that is causing teh error, not the one you assign to.