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Function.h

Go to the documentation of this file.

#ifndef Impala_Visualisation_Plot_Function_h
#define Impala_Visualisation_Plot_Function_h

#include "Visualization/Plot/Plottable.h"

namespace Impala
{
namespace Visualization
{
namespace Plot
{

class Weibull : public Plottable
{
public:

    Weibull(double z, double beta, double gamma, int sampleCount=100)
    {
        mBeta = beta;
        mGamma = gamma;
        mSampleCount = sampleCount;
        mZ = z;
        ComputeScaling();
    }

    virtual void
    Draw(Plot* plot)
    {
        double l,t,r,b;
        plot->GetRange(l,t,r,b);
        double dx=(r-l)/mSampleCount;

        SelectColor();

        BeginSampling();
        glBegin(GL_LINE_STRIP);
        for (double x=mMinX ; x<mMaxX ; x+=dx)
            glVertex3d(x, Sample(x), mZ);
        glEnd();
        EndSampling();
    }

    virtual void
    BeginSampling() 
    {
    }
    
    virtual double
    Sample(double x) 
    {
        return exp(-pow(fabs((x-mMu)/mBeta), mGamma)) * mScaling;
    }

    virtual void
    EndSampling() 
    {
    }

    void
    SetParams(double beta, double gamma, double mu)
    {
//        std::cout << "b: " << beta << " g: " << gamma << std::endl;
        mBeta = beta;
        mGamma = gamma;
        mMu = mu;
        ComputeScaling();
    }

    double
    GetParams(double& beta, double& gamma, double& mu)
    {
        beta = mBeta;
        gamma = mGamma;
        mu = mMu;
    }

protected:

    int mSampleCount;
    double mZ;
    double mBeta, mGamma, mMu;
    double mScaling;

    void
    ComputeScaling()
    {
        // the weibull function should be scaled by
        // gamma / (2*beta*GAMMA(1/gamma))
        // where GAMMA is the gamma function (faculty for rational numbers)

        mScaling = mGamma;
        mScaling /= 2.*mBeta*pow(mGamma,1./mGamma)*GammaFunc(1./mGamma);
        SetDimensionsY(0, mScaling);
    }

    double
    GammaFunc(double xx)
    {
        // I could only find a log gamma from "numerical recipes"
        // http://www.library.cornell.edu/nr/cbookcpdf.html
        double x,y,tmp,ser;
        static double cof[6] =
        {
            76.18009172947146, -86.50532032941677,
            24.01409824083091, -1.231739572450155,
            0.1208650973866179e-2, -0.5395239384953e-5
        };

        int j;
        y=x=xx;
        tmp=x+5.5;
        tmp -= (x+0.5)*log(tmp);
        ser=1.000000000190015;
        for (j=0;j<=5;j++)
            ser += cof[j]/++y;
        xx = -tmp+log(2.5066282746310005*ser/x);
        return exp(xx);
    }

};

}//namespace Impala
}//namespace Visulization
}//namespace Plot

#endif Impala_Visualisation_Plot_Function_h

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