You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: tutorial_ClassRF.m
    path of file: ./repos/Image-Harmonization-Dataset-iHarmony4/Xue et al/demo/rf_class_c
    
    the code of the file until where you have to start completion: % A simple tutorial file to interface with RF
% Options copied from http://cran.r-project.org/web/packages/randomFo
    
function

    model = classRF_train(X_trn,Y_trn, 100, 4, extra_options);
    Y_hat = classRF_predict(X_tst,model);
    fprintf('\nexample 6: error rate %f\n',   length(find(Y_hat~=Y_tst))/length(Y_tst));

% example 7: modify to make class(es) more IMPORTANT than the others
    %  extra_options.cutoff (Classification only) = A vector of length equal to
    %                       number of classes. The 'winning' class for an observation is the one with the maximum ratio of proportion
    %                       of votes to cutoff. Default is 1/k where k is the number of classes (i.e., majority
    %                       vote wins).    clear extra_options;
    extra_options.cutoff = [1/4 3/4]; %for the [-1 +1] classses in twonorm
    % if you sort the labels in training and arrange in ascend