fitcecoc，svm培训出错

Question

 trainingSet =  imageSet(imgFolder1, 'recursive');

  % Using HOG Features

 cellSize = [4 4];
 hogFeatureSize = length(hog_4x4);

   %% Train a Digit Classifier

 trainingFeatures = [];
 trainingLabels   = [];

 for digit = 1:numel(trainingSet)

 numImages = trainingSet(digit).Count;           
features  = zeros(numImages, hogFeatureSize, 'single');

for i = 1:numImages

    img = read(trainingSet(digit), i);

    % Apply pre-processing steps
    lvl = graythresh(img);
    img = im2bw(img, lvl);        

    features{i}= extractHOGFeatures(img, 'CellSize', cellSize);
end
 labels= repmat(trainingSet(digit).Description, numImages, 1);

   trainingFeatures=[training features; features];
 trainingLabels=[trainingLabels; labels];

 end

 Classifier=fitcecoc(trainingFeatures, training labels);

我正在尝试使用上面的代码训练svm分类器。

我在分类器行遇到错误，说

fitcecoc出错：obj = fit（temp，X，Y）;

... X必须是数字矩阵

我不知道该怎么办。请帮忙