All the options that you see in the Classification Learner App have functional equivalents as well. All those functions are tucked under this page: https://www.mathworks.com/help/stats/classification.html You will see hyperlinks to different approaches: Nearest Neighbour, Naive Bayes, Trees, SVMs, etc. Each page will have a list of all the functions available for that method.
A simple approach to quickly figure out the functional equivalent of an option in the app is to use the "Generate Function" option from the tool strip on the Classification Learner App. This generates a MATLAB function file with a call to the function for the classification method of your choice. Hope this helps you get started.
