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