Hi Jong-II,
Predictor and response variables in MATLAB can be of various types, including numeric, categorical, string, or logical vectors, as well as cell arrays of character arrays. The response variable should not contain more than 500 unique class labels. You can check if your input data matches the above mentioned categories. A 10000*1 variable is valid as a response variable in a classification task, assuming it satisfies the mentioned categories. For more information on selecting data and understanding the constraints, you can refer to the documentation link provided below:-
The issue you're experiencing may also arise if some targets are present in the testing dataset but not in the training dataset. You can ensure that all targets included in the testing set are also present in the training set. You can also utilize the MATLAB Central discussion link provided below:-
