The end operator must be used within an array index expression

Question

My output is showing "The end operator must be used within an array index expression." when I try to run this:     %15. split spectograms of background noise between the training, validation, and test sets numTrainBkg = floor(0.85*numBkgClips); numValidationBkg = floor(0.15*numBkgClips); XTrain(:,:,:,end+1:end+numTrainBkg) = Xbkg(:,:,:,1:numTrainBkg); YTrain(end+1:end+numTrainBkg) = "background"; XValidation(:,:,:,end+1:end+numValidationBkg) = Xbkg(:,:,:,numTrainBkg+1:end); YValidation(end+1:end+numValidationBkg) = "background";

John Williams · Accepted Answer

You cannot use end in a variable that has not yet been created. Here, you are using end in the assignment to all your variables. Since they don't exist yet, you get an error. Consider this example.
 
 
a(end)=1
The end operator must be used within an array index expression.
Perhaps you meant to do this:
numTrainBkg = floor(0.85*numBkgClips);
numValidationBkg = floor(0.15*numBkgClips);

XTrain = Xbkg(:,:,:,1:numTrainBkg);
YTrain(1:numTrainBkg) = "background";
XValidation = Xbkg(:,:,:,numTrainBkg+1:end);
YValidation(1:numValidationBkg) = "background";

The end operator must be used within an array index expression

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