histogram functionality

[Andy Panov]

Hi ediap,

I have noticed, it++ lacks histogram functionality in stat.h. I have got a template class implementing histogram computations. Please let me know if you are intersted in integrating it into the library.

/*!
\file
\brief Class for Histogram computation
\author Andy Panov

$Revision: $

$Date: $
*/

ifndef __histogram_h

define __histogram_h

include "base/matfunc.h"

include "base/vec.h"

namespace itpp{
//! \addtogroup statistics
//!@{

/*! 
\brief A class for the histogram computation
*/

template<class T> class Histogram{
public:
    //! Constructor constructs histogram with 100 bins by default spanning values from 0 to 99
    Histogram(T from = 0, T to = 99, int n_bins = 100);
    //! Virtual destructor
    virtual ~Histogram(){};
    //! Histogram update
    void update(T value);
    //! Bins reset, so accumulation can be restarted
    void reset(){trials_cnt = 0;bins.zeros();};
    //! Access to single bin
    int get_bin(int ix) const {return bins[ix];};
    //! Access to histogram as a vector
    ivec get_bins() const {ivec ret = bins; return ret;};
    //! Access to bin centers
    Vec<T> get_bin_vals()const {Vec<T> ret = center_vals; return ret;};
    T get_bin_val(int ix)const {return center_vals[ix];};
    //! Experimental Probability Density Function (PDF) computation
    vec get_pdf() const;
    //! Experimental Cumulative Density Function (CDF) computation  
    vec get_cdf() const;
    //! Current number of bins
    int bins_num() const {return num_bins;};

private:
    //! Number of processed samples
    int trials_cnt;
    //! Number of bins
    int num_bins;
    //! Step between bins
    T step;
    //! Low boundaries of histogram bins
    Vec<T> low_vals;
    //! Upper boundaries of histogram bins
    Vec<T> hi_vals;
    //! Bin centers
    Vec<T> center_vals; 
    //! Bins storage
    ivec bins;
};

template<class T>
inline Histogram<T>::Histogram(T from, T to, int n_bins): num_bins(n_bins), low_vals(n_bins),
                            hi_vals(n_bins),center_vals(n_bins),bins(n_bins),trials_cnt(0){
            step = (to - from)/(num_bins-1);
            center_vals = linspace(from,to,num_bins);
            low_vals = center_vals - step/2; 
            hi_vals = center_vals + step/2; 
            reset();
}

//
//Histogram methods. Inlining is used to speed things up.
//
template<class T>
inline void Histogram<T>::update(T value){        
        //search for the corresponding bin
        //using dichotomy approach
        int start = 0;
        int end = num_bins - 1;
        int test = (start + end)/2;;
        while(start < end){
            if(value < low_vals[test])
                end = test-1;
            else if(value >= hi_vals[test])
                start = test+1;
            else
                break;
            test = (start + end)/2;
        };


        bins[test] +=1;
        trials_cnt++;
}

template<class T>
inline vec Histogram<T>::get_pdf() const {
        vec pdf(num_bins);
        for (int j =0; j < num_bins; j++)
            pdf[j] = static_cast<double>(bins[j])/trials_cnt;
        return pdf;
}

template<class T>
inline vec Histogram<T>::get_cdf() const {
        ivec tmp = cumsum(bins);            
        vec cdf(num_bins);
        for (int j =0; j < num_bins; j++)
            cdf[j] = static_cast<double>(tmp[j])/trials_cnt;      
        return cdf; 
}

}

endif //#ifndef __histogram_h

Best regards.
Andy.

[Andy Panov]

Hi Adam

I gonna put the source to the Feature Requests tracker tomorrow.

Best Regards.
Andy.

[Adam Piątyszek]

Hi Andy,

Thanks for your contribution. Of couse, we are open to include new functions and classes to the IT++ library. But first we need to check out if everything new fits IT++ and works as expected.

To help us, could you please post a patch or a new file to the Feature Requests tracker, so your contribution will not get lost in the forum threads.

Thanks in advance!

BR,

/ediap