The end operator must be used within an array index expression

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";

Please help me solve this..

[Stephen23]

@Sharena Natasha Nor Hisham: please show us the complete error message. This means all of the red text.

[Sharena Natasha Nor Hisham]

@Stephen This is the whole red text shown:

The end operator must be used within an array index expression.

[Voss]

Please run the following command from within the scope where these variables are defined (i.e., I don't know if this is in a function or a script; if it's a function put this line in the function after where the variables are defined and before where the error happens; if it's a script you can just run this line on the MATLAB command prompt):

whos XTrain YTrain XValidation YValidation Xbkg

and show the output. This will tell us what type of variables these are. It seems like at least one of them is not an array.

[Sharena Natasha Nor Hisham]

@Benjamin this is the output:

Name Size Bytes Class Attributes

XTrain 98x50x1x170 3332000 single

XValidation 98x50x1x30 588000 single

Xbkg 98x50x1x200 3920000 single

YTrain 2856x1 4534 categorical

YValidation 1064x1 2742 categorical

[Sharena Natasha Nor Hisham]

but now i'm facing another issue after I tried training the network:

Error using trainNetwork (line 184)

Number of observations in X and Y disagree.

[Cris LaPierre]

Please create a new question for this as it is unrelated.

Answer 1

[Cris LaPierre]

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";

I've never used it on a 4D array, but you may want to look into using cvpartition.

[Sharena Natasha Nor Hisham]

Ahh I understand it now. I tried running the command you gave. And it worked! Thank you so much