Invalid RHS for assignment to a categorical array.

function [result] = multisvm(TrainingSet,Group_Train1,TestSet,actual_label)

%Models a given training set with a corresponding group vector and 
%classifies a given test set using an SVM classifier according to a 
%one vs. all relation. 
%
%This code was written by Cody Neuburger [e-mail]
%Florida Atlantic University, Florida USA...



%This code was adapted and cleaned from Anand Mishra's multisvm function
%found at http://www.mathworks.com/matlabcentral/fileexchange/33170-multi-class-support-vector-machine/

u=unique(Group_Train1);
numClasses=length(u);
result = categorical.empty();

%result = zeros(length(TestSet(:,1)),1);


%build models
models = cell(numClasses,1);
for k=1:numClasses
    %Vectorized statement that binarizes Group
    %where 1 is the current class and 0 is all other classes
    G1vAll=(Group_Train1==u(k));
    models{k} = fitcsvm(TrainingSet,G1vAll,'KernelFunction','polynomial','polynomialorder',3,'Solver','ISDA','Verbose',0,'Standardize',true);

    if ~models{k}.ConvergenceInfo.Converged
        fprintf('Training did not converge for class "%s"\n', string(u(k)));
        
    end
    
    
end

%classify test cases
for t=1:size(TestSet,1)
   matched = false;
   for k = numClasses:-1:1
    % for k =1: numClasses
    
          if(predict(models{k},TestSet(t,: ))) 

         matched = true;
           break;
        end

    end
   if matched
   result(t,1) = u(k);
   %result(t) = u(k);

   else
   result(t,1) = 'No Match';
    
%--------------------------------
   end
end
%Accuracy = mean(Group_Test1==result) * 100;
%fprintf('Accuracy = %.2f\n', Accuracy);
%fprintf('error rate = %.2f\n ', mean(result ~= Group_Test1 ) * 100);
%confusionchart(Group_Test1, result);

end

>> HOG2

Error using categorical/subsasgn (line 72)

Invalid RHS for assignment to a categorical array.

Error in multisvm (line 52)

result(t,1) = u(k);

Error in HOG2 (line 30)

result= multisvm(Feat1,Group_Train1,Feat2,actual_label);

Answer 1

[Jan]

Group_Train1 is a [274x1] double vector. u contains its unique elements. result is an empty categorical.

The error message means, that you cannot insert scalar doubles into an array of categoricals:

result = categorical.empty();
result(1) = 19  % FAIL

Error using ()
Right hand side of an assignment to a categorical array must be a categorical or text representing a category name.

I'm confused by the different error message. Which Matlab version do you use?

[sun rise]

2019a