How to solve the SVMTRAIN 's groups error?

I am using SVM classifier for binary classification(class labels are 0 and 1) by using this code:

mysvm=svmtrain(xtrain,ytrain,'kernel_function','linear','boxconstraint',2);
    sv=svmclassify(mysvm,xtest);

but Matlab shows this error

    Error using svmtrain (line 275)
SVMTRAIN only supports classification into two groups. GROUP contains 50 groups.

I'll be very grateful to have your opinions how to solve this error.

Thanks

[Image Analyst]

Supply just two groups (columns).

[phdcomputer Eng]

@Image Analyst Thanks

my classification code is:

rows=(1:n);
test_count=floor((0.2)*n);
[n,m]=size(data0);
test_rows=randsample(rows,test_count);
train_rows=setdiff(rows,test_rows);
test=data0(test_rows,:);
train=data0(train_rows,:);
xtest=test(:,1:m-1);
ytest=test(:,m);
xtrain=train(:,1:m-1);
ytrain=train(:,m);
output_svm= classificationa(xtest,xtrain,ytrain);

and then by comparing xtrain&ytrain with xtest, I obtain the resault of svm classifier.

In this code, n=62 and m=30 so test_count=12 , test is a 12x30 matrix and train is a 50x30 matrix

so in the error, 50 groups is because of train matrix:

    Error using svmtrain (line 275)
SVMTRAIN only supports classification into two groups. GROUP contains 50 groups.

but I don't know how to solve this error as you said Supplying just two groups (columns). I'll be very grateful to have your opinion how to change the number of groups, should I change the the above classification codes?