00001
00012 #ifdef _MSC_VER
00013 #include "msdevstudio/MSconfig.h"
00014 #endif
00015
00016 #include "PowerLaw.h"
00017
00018 #include "FunctionHelper.h"
00019
00020 #include <cmath>
00021 #include <cassert>
00022
00023 #ifdef ITERATOR_MEMBER_DEFECT
00024 using namespace std;
00025 #else
00026 using std::max;
00027 using std::vector;
00028 #endif
00029
00030 namespace hippodraw {
00031
00032 PowerLaw::PowerLaw ( )
00033 {
00034 initialize ();
00035 }
00036
00037 PowerLaw::PowerLaw ( double prefactor, double index )
00038 {
00039 initialize ();
00040
00041 m_parms[0] = prefactor;
00042 m_parms[1] = index;
00043 }
00044
00045 void PowerLaw::initialize ()
00046 {
00047 m_name = "PowerLaw";
00048 m_parm_names.push_back ( "Prefactor" );
00049 m_parm_names.push_back ( "Index" );
00050
00051 resize ();
00052 }
00053
00054 FunctionBase * PowerLaw::clone () const
00055 {
00056 return new PowerLaw ( *this );
00057 }
00058
00059 double PowerLaw::operator () ( double x ) const
00060 {
00061 return m_parms[0]*pow(x, m_parms[1]);
00062 }
00063
00064
00065 void
00066 PowerLaw::
00067 initialParameters ( const FunctionHelper * helper )
00068 {
00069 double min_x = helper->minCoord ();
00070 double max_x = helper->maxCoord ();
00071 max_x = (min_x + max_x)/2.;
00072
00073 double min_y, max_y;
00074 try {
00075 min_y = helper->valueAt(min_x);
00076 max_y = helper->valueAt(max_x);
00077 if (min_y != 0 && max_y != 0) {
00078 m_parms[1] = log( max_y/min_y ) / log( max_x/min_x );
00079 m_parms[0] = max_y/pow(max_x, m_parms[1]);
00080 return;
00081 }
00082 } catch (...) {
00083
00084 }
00085
00086
00087 min_y = max(helper->minValue(), 1.);
00088 max_y = helper->maxValue();
00089 m_parms[1] = log( max_y/min_y ) / log( max_x/min_x );
00090 m_parms[0] = max_y/pow(max_x, m_parms[1]);
00091 }
00092
00093 double PowerLaw::derivByParm ( int i, double x ) const
00094 {
00095 switch ( i ) {
00096 case 0 :
00097 return pow(x, m_parms[1]);
00098 break;
00099
00100 case 1 :
00101 return m_parms[0]*pow(x, m_parms[1])*log(x);
00102 break;
00103
00104 default:
00105 assert ( false );
00106 break;
00107 }
00108 return 0.0;
00109 }
00110
00111 }
00112