smooth filter

gistfile1.cpp

//
//  BoxFIR.h
//  FilteringTrial
//
//  Created by Akira on 5/18/13.
//
//

#ifndef FilteringTrial_BoxFIR_h
#define FilteringTrial_BoxFIR_h

/*
 Boxcar finite impulse response filter.
 http://en.wikipedia.org/wiki/Boxcar_function
 http://en.wikipedia.org/wiki/Window_function#Rectangular_window
 */

class BoxFIR
{
    int numCoeffs; //MUST be > 0
    vector<double> b; //Filter coefficients
    vector<double> m; //Filter memories
    
public:
    
    BoxFIR(int _numCoeffs):
    
    numCoeffs(_numCoeffs)
    {
        if (numCoeffs<1)
            numCoeffs = 1; //Must be > 0 or bad stuff happens
        
        double val = 1./numCoeffs;
        for (int ii=0; ii<numCoeffs; ++ii) {
            b.push_back(val);
            m.push_back(0.);
        }
    }
    
    void filter(vector<double> &a)
    {
        double output;
        
        for (int nn=0; nn<a.size(); ++nn)
        {
            //Apply smoothing filter to signal
            output = 0;
            m[0] = a[nn];
            for (int ii=0; ii<numCoeffs; ++ii) {
                output+=b[ii]*m[ii];
            }
            
            //Reshuffle memories
            for (int ii = numCoeffs-1; ii!=0; --ii) {
                m[ii] = m[ii-1];
            }
            a[nn] = output;
        }
    }
    
    
};


#endif



    BoxFIR box(2); //If this is 1, then no filtering happens, use bigger ints for more smoothing
    
    //Make a rising saw function for demo
    vector<double> a;
    a.push_back(0.); a.push_back(0.25); a.push_back(0.5); a.push_back(0.75); a.push_back(1.);
    a.push_back(0.); a.push_back(0.25); a.push_back(0.5); a.push_back(0.75); a.push_back(1.);
    a.push_back(0.); a.push_back(0.25); a.push_back(0.5); a.push_back(0.75); a.push_back(1.);
    a.push_back(0.); a.push_back(0.25); a.push_back(0.5); a.push_back(0.75); a.push_back(1.);
    
    box.filter(a);
    
    for (int nn=0; nn<a.size(); ++nn)
    {
        cout << a[nn] << endl;
    }