Please post useful details. What exactly is "mat", which format does it have, and to which type of data do you want to convert it? Why do you need a loop?
You participate in the forum for a long time now. We can expect that you know and consider https://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer. You can reduce the need for questions for clarifications by providing the details. Remember that the readers do not have the faintest idea about what you are doing, because they cannot read your mind. Posting questions, which require to guess all details, wastes your time and the time of the readers.
