Your implementation looks correct, except just one thing; "svmtrain" has been deprecated.
As a replacement, "fitcsvm" function has been introduced. Here is an example:
features_train = xlsread('A_B_features');
[num, txt] = xlsread('A_B_labels');
labels_train = categorical(txt);
SVMModel = fitcsvm(features_train, labels_train, 'KernelFunction', 'linear', 'Standardize', true, 'ClassNames', {'A', 'B'});
Here is the documentation link for "fitcsvm":
Hope this helps.
