Dimensions of arrays being concatenated are not consistent error.

How to fix this error?

Error using HelperTestKNNClassifier (line 35)

Could not concatenate the table variable 'ActualSpeaker' using VERTCAT.

Caused by:

Error using vertcat

Dimensions of arrays being concatenated are not consistent.

for idx = 1:length(Filenames)
    T = featuresTest(Fidx==idx,2:end);  % Rows that correspond to one file
    predictedLabels = string(predict(trainedClassifier,T(:,1:15))); % Predict
    totalVals = size(predictedLabels,1);

    [predictedLabel, freq] = mode(categorical(predictedLabels)); % Find most frequently predicted label
    match = freq/totalVals*100;

    result_file.Filename = Filenames(idx);
    result_file.ActualSpeaker = T.Label{1};
    result_file.PredictedSpeaker = char(predictedLabel);
    result_file.ConfidencePercentage = match;
    
    result = [result; struct2table(result_file)]; %#ok
end

[per isakson]

See: Debug a MATLAB Program and Examine Values While Debugging

Answer 1

[dpb]

result_file.ActualSpeaker = T.Label{1};
...
result = [result; struct2table(result_file)];

You're trying to catenate char() arrays that may not be the same length (and, in fact, aren't). This happened because you first dereference a cell string to char, then tried to build a table. Illustration of barebones problem:

>> T.Label='Label 1';          % first char label (did the {} dereference manually)
>> res=struct2table(T);        % first entry into a table is ok...
>> T.Label='Label 1001';       % later on the string is longer...
>> res=[res;struct2table(T)]   % and, BOOM!
Could not concatenate the table variable 'Label' using VERTCAT.
Caused by:
    Error using vertcat
    Dimensions of matrices being concatenated are not consistent. 
>> 

The solution is to not dereference the label but leave as cell strings (or, if appropriate, convert to categorical )

result_file.ActualSpeaker = T.Label(1);