SphericalVariogram.cpp

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#ifdef HAVE_CONFIG_H
   #include <config.h>
#else
#error "Cannot compile with HAVE_CONFIG_H symbol! run configure first!"
#endif
 
#include "../classes.h"
#include "../../shared/shared.h"
 
/*SphericalVariogram constructors and destructor*/
SphericalVariogram::SphericalVariogram(){/*{{{*/
   this->nugget = 0.2;
   this->sill   = 1;
   this->range  = SQRT3;
   return;
}
/*}}}*/
SphericalVariogram::SphericalVariogram(Options* options){/*{{{*/
 
   /*Defaults*/
   this->nugget = 0.2;
   this->sill   = 1;
   this->range  = SQRT3;
 
   /*Overwrite from options*/
   if(options->GetOption("nugget")) options->Get(&this->nugget,"nugget");
   if(options->GetOption("sill"))   options->Get(&this->sill,"sill");
   if(options->GetOption("range"))  options->Get(&this->range,"range");
 
   /*Checks*/
   if(nugget==sill) _error_("nugget and sill cannot be equal (constant semivariogram not allowed)");
}
/*}}}*/
SphericalVariogram::~SphericalVariogram(){/*{{{*/
   return;
}
/*}}}*/
 
/*Object virtual functions definitions:*/
Object* SphericalVariogram::copy(void){/*{{{*/
   return new SphericalVariogram(*this);
}
/*}}}*/
void SphericalVariogram::Echo(void){/*{{{*/
   _printf_("SphericalVariogram\n");
   _printf_("   nugget: " << this->nugget << "\n");
   _printf_("   sill  : " << this->sill << "\n");
   _printf_("   range : " << this->range << "\n");
}
/*}}}*/
 
/*Variogram function*/
double SphericalVariogram::Covariance(double deltax,double deltay){/*{{{*/
   /*The covariance can be deduced from the variogram from the following
    * relationship:
    *    2 gamma = C(x,x) + C(y,y) -2 C(x,y)
    * so
    *    C(h) = sill - gamma                                            */
   double h,cova;
 
   /*Calculate length square*/
   h=sqrt(deltax*deltax + deltay*deltay);
 
   /*return covariance*/
   if(h<=range)
    cova = (sill-nugget)*(1 - (3*h)/(2*range) + pow(h,3)/(2*pow(range,3)) );
   else
    cova = 0.;
 
   return cova;
}
/*}}}*/
double SphericalVariogram::SemiVariogram(double deltax,double deltay){/*{{{*/
   /*http://en.wikipedia.org/wiki/Variogram*/
   double h,gamma;
 
   /*Calculate length square*/
   h=sqrt(deltax*deltax + deltay*deltay);
 
   /*return semi-variogram*/
   if(h<=range)
    gamma = (sill-nugget)*( (3*h)/(2*range) - pow(h,3)/(2*pow(range,3)) ) + nugget;
   else
    gamma = sill;
 
   return gamma;
}
/*}}}*/