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Starting to use

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This commit is contained in:
Peter Boyle 2015-06-09 22:38:13 +01:00
parent 2e6986892a
commit 6fb36c8a51
1 changed files with 12 additions and 4 deletions
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16
lib/algorithms/approx/Chebyshev.h
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@ -42,6 +42,14 @@ namespace Grid {
double lo; double lo;
public: public:
void csv(std::ostream &out){
for (double x=lo; x<hi; x+=(hi-lo)/1000) {
double f = approx(x);
out<< x<<" "<<f<<std::endl;
}
return;
}
Chebyshev(double _lo,double _hi,int _order, double (* func)(double) ){ Chebyshev(double _lo,double _hi,int _order, double (* func)(double) ){
lo=_lo; lo=_lo;
hi=_hi; hi=_hi;
@ -52,16 +60,16 @@ namespace Grid {
for(int j=0;j<order;j++){ for(int j=0;j<order;j++){
double s=0; double s=0;
for(int k=0;k<order;k++){ for(int k=0;k<order;k++){
double y=cos(M_PI*(k+0.5)/order); double y=std::cos(M_PI*(k+0.5)/order);
double x=0.5*(y*(hi-lo)+(hi+lo)); double x=0.5*(y*(hi-lo)+(hi+lo));
double f=func(x); double f=func(x);
s=s+f*cos( j*M_PI*(k+0.5)/order ); s=s+f*std::cos( j*M_PI*(k+0.5)/order );
} }
Coeffs[j] = s * 2.0/order; Coeffs[j] = s * 2.0/order;
} }
}; };
double Evaluate(double x) // Convenience for plotting the approximation double approx(double x) // Convenience for plotting the approximation
{ {
double Tn; double Tn;
double Tnm; double Tnm;
@ -91,7 +99,7 @@ namespace Grid {
void PlotApprox(std::ostream &out) { void PlotApprox(std::ostream &out) {
out<<"Polynomial approx ["<<lo<<","<<hi<<"]"<<std::endl; out<<"Polynomial approx ["<<lo<<","<<hi<<"]"<<std::endl;
for(double x=lo;x<hi;x+=(hi-lo)/50.0){ for(double x=lo;x<hi;x+=(hi-lo)/50.0){
out <<x<<"\t"<<Evaluate(x)<<std::endl; out <<x<<"\t"<<approx(x)<<std::endl;
} }
}; };