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Print histogram values for image in BOW

Hi.

I'm working on Bag of words program. I have extracted descriptors for each image via SiftFeatureDetector and SiftDescriptorExtractor into BOWKMeansTrainer as follows:

featureDetector->detect(image, keypoints);
descriptorExtractor->compute(image, keypoints, descriptors);
bowTrainer.add(descriptors);

and runs BOWKMeansTrainer::cluster() and BOWImgDescriptorExtractor::setVocabulary() after. Then I want to see how does the histograms computed via BOWImgDescriptorExtractor looks like for some of the images (reduced code):

bowDE->compute(image, keypoints, histogram);
for (int i = 0; i < histogram.cols; i++)
    cout << histogram.at<unsigned>(0, i) << ",";

Result looks like:

{[0,997286537,988897929,1001720295,0,0,1014063753,0, ...]}

(rows=1, cols=count_of_visual_words) So there are either zeros or really huge numbers. Maybe I didn't understand something. How can I correctly print histogram values for given image?