That "eval" function was a method of the "classregtree" class which was removed in MATLAB R2018a. I noticed that you are now using the "fitctree" method instead of the removed "classregtree".
The trees from "fitctree" are part of the "ClassificationTree" class. A similar method to "eval" is in that class. It is called- "predict" and it predicts labels using classification tree. The third input in "predict" is slightly different than "eval", so you would need to change the inputs slightly.
Instead of:
>> eval(T, X, s)
The "predict" function should be used with the 'Subtrees' Name-Value pair.
>> predict(T, X, 'Subtrees', s);
For more information on the "ClassificationTree" class and the "predict" function, see the documentation links below:
