[Kaldi-developers] Maybe there is an error in src/nnet/nnet-various.h-MomentStatistics(const Vector<Real> &vec)

[李飞腾 <fei...@yo...>]

Hi:

I think the way to computer variance in MomentStatistics() is not right. 
variance-wiki http://en.wikipedia.org/wiki/Variance 
using ApplyPow() to replace vec_aux.MulElements(vec); 

std::string MomentStatistics(const Vector<Real> &vec) {
  // we use an auxiliary vector for the higher order powers
  Vector<Real> vec_aux(vec);
  // mean
  Real mean = vec.Sum() / vec.Dim();
  // variance
  vec_aux.Add(-mean);
  vec_aux.ApplyPow(2.0); //vec_aux.MulElements(vec); // (vec-mean)^2
  Real variance = vec_aux.Sum() / vec.Dim();
  vec_aux.ApplyPow(3.0/2.0); //vec_aux.MulElements(vec); // (vec-mean)^3
  Real skewness = vec_aux.Sum() / pow(variance, 3.0/2.0) / vec.Dim();
  vec_aux.ApplyPow(4.0/3.0); //vec_aux.MulElements(vec); // (vec-mean)^4
  Real kurtosis = vec_aux.Sum() / (variance * variance) / vec.Dim() - 3.0;
  // send the statistics to stream,
  std::ostringstream ostr;
  ostr << " ( min " << vec.Min() << ", max " << vec.Max()
       << ", mean " << mean 
       << ", variance " << variance 
       << ", skewness " << skewness
       << ", kurtosis " << kurtosis
       << " ) ";
  return ostr.str();
}

Am I right?

What is the easiest way to contribute to kaldi?

Best！
feiteng li