Function PCA

src/examples/python/streaming_extractor/streaming_extractorutils.cpp:208–244

void PCA(Pool& pool, const string& nspace) {

  // namespace:
  string llspace = "lowlevel.";
  if (!nspace.empty()) llspace = nspace + ".lowlevel.";

  vector<vector<Real> > sccoeffs = pool.value<vector<vector<Real> > >(llspace + "sccoeffs");
  vector<vector<Real> > scvalleys = pool.value<vector<vector<Real> > >(llspace + "scvalleys");

  Pool poolSc, poolTransformed;

  for (int iFrame = 0; iFrame < (int)sccoeffs.size(); iFrame++) {
    vector<Real> merged(2*sccoeffs[iFrame].size(), 0.0);
    for(int i=0, j=0; i<(int)sccoeffs[iFrame].size(); i++, j++) {
      merged[j++] = sccoeffs[iFrame][i];
      merged[j] = scvalleys[iFrame][i];
    }
    poolSc.add("contrast", merged);
  }

  standard::Algorithm* pca  = standard::AlgorithmFactory::create("PCA",
                                             "namespaceIn",  "contrast",
                                             "namespaceOut", "contrast");
  pca->input("poolIn").set(poolSc);
  pca->output("poolOut").set(poolTransformed);
  pca->compute();

  pool.set(llspace + "spectral_contrast.mean",
           meanFrames(poolTransformed.value<vector<vector<Real> > >("contrast")));
  pool.set(llspace + "spectral_contrast.var",
           varianceFrames(poolTransformed.value<vector<vector<Real> > >("contrast")));

  // remove original data from spectral contrast:
  pool.remove(llspace + "sccoeffs");
  pool.remove(llspace + "scvalleys");
  delete pca;
}

// Add missing descriptors which are not computed yet, but will be for the
// final release or during the 1.x cycle. However, the schema need to be