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SVM Training Data with Bag-of-Word

asked 2016-12-18 14:08:14 -0500

marcob88 gravatar image

Hi, I've a question with training an SVM multiclass with bag of word model. I have 50 video of training and each video is represented by a matrix of words.

Now i have a vector<mat> that contains all training data. How can training svm with this data structure?

I think to use pca but i'm not sure if is the exactly way.

Thanks

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May be you can try this example

LBerger gravatar imageLBerger ( 2016-12-18 14:34:11 -0500 )edit

^^ for opencv2.4

berak gravatar imageberak ( 2016-12-19 03:58:47 -0500 )edit
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for opencv 3.1 it's here

LBerger gravatar imageLBerger ( 2016-12-19 04:02:45 -0500 )edit

^^ cool :)

berak gravatar imageberak ( 2016-12-19 04:09:30 -0500 )edit

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answered 2016-12-19 03:58:59 -0500

berak gravatar image

updated 2016-12-19 08:54:03 -0500

to train an SVM with opencv3, you'd go like this:

// preprocess data:
vector<Mat> fromBOW = ...;
Mat data, labels; // initially empty
for (size_t i=0; i<fromBOW.size(); i++) {
      Mat m;
      fromBOW.convertTo(m, CV_32F); // we need float features
      data.push_back(m.reshape(1,1)); // add as a single, flat row vec.

      int label = 17; // ??? how do you get your labels ????
      labels.push_back(label);
}

then we can train the SVM:

Ptr<ml::SVM> svm = ml::SVM::create();
svm->setKernel(ml::SVM::LINEAR);
bool itWorked = svm->train(data, ml::ROW_SAMPLE, labels);

later, we can predict on bow features:

Mat bowfeature = ...
Mat m;
bowfeature .convertTo(m, CV_32F); // we need float features
int predicted = svm->predict(m.reshape(1,1)); // single, flat row vec.
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But if every mat have different size? For example i have a mat with 7 rows (number frame of video) and 10 cols ( number of words) but another mat can have different size...how can train in this situation? is possible?

marcob88 gravatar imagemarcob88 ( 2016-12-20 15:31:57 -0500 )edit

hmm, can it be, you got the BoW idea wrong ?

berak gravatar imageberak ( 2016-12-20 16:38:03 -0500 )edit

could you try to edit your question, and be more explicit about the data you have ? what format ? a "matrix of words" is what, exactly ?

berak gravatar imageberak ( 2016-12-21 00:52:24 -0500 )edit
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Asked: 2016-12-18 14:08:14 -0500

Seen: 123 times

Last updated: Dec 19 '16