Error using svm classifier

Error using svmtrain (line 274) SVMTRAIN only supports classification into two groups. GROUP contains 4 groups.

Error in Classifier_10_fold (line 15) svmModel = svmtrain(FM(trainIdx,:), groups(trainIdx), ...

Answer 1

[KSSV]

svm will work on only two classes or groups. You need to send only two groups data to train it. Check the below example:

load fisheriris
% the data has three classes, pick only two classes out of it. 
inds = ~strcmp(species,'setosa');     % don't consider this class 
X = meas(inds,3:4);
y = species(inds);
%
SVMStruct = svmtrain(X,y)

Where as if I use all the classes, it will throw the same error as you got .

SVMStruct = svmtrain(meas,species) ;  % this will give error as three classes are present

Also check that svmtrain is outdated, you need to use fitcsvm.

[Basavaraja V]

sir, how to do for multi classes or groups

[KSSV]

YOu select any two groups and run the model. You can select the group using:

load fisheriris
% the data has three classes, pick only two classes out of it. 
inds = strcmp(species,'setosa') | strcmp(species,'virginica');    % select these two out of all groups     

X = meas(inds,3:4);
y = species(inds);
%
SVMStruct = svmtrain(X,y) ;

[Walter Roberson]

https://www.mathworks.com/help/stats/classificationecoc-class.html