矩阵连接错误

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

我需要帮助，当我运行上面的代码时，我会在＃features（i，:)中看到错误（说明分配维度不匹配）。

我实际上是尝试从大约20幅图像中提取HOG特征，并且我发现它们提取的图像数量不同。请问如何解决这个问题。谢谢。