I am attempting to use the polynomial interpolation method with GSL. However I
am getting very strange results.
If I run the attached program I get the below result. If I change the method to
linear or cspline the interpolation works fine.
Not in previous gsl versions the polynomial interpolation has worked!
[cid:[email protected]]
Is there something I am missing?
Yours aye
Adam
#include <iostream>
#include <gsl/gsl_vector.h>
#include <gsl/gsl_errno.h>
#include <gsl/gsl_spline.h>
using namespace std;
int main(int argc, char *argv[])
{
double x[1001];
double y[1001];
for(int p=0;p<1001;p++) {
x[p] = double(p) *0.01;
y[p] = x[p] *x[p];
}
gsl_interp_accel* acc ;
gsl_spline* spline;
//gsl_interp_linear
//gsl_interp_polynomial
//gsl_interp_cspline
spline = gsl_spline_alloc( gsl_interp_polynomial , 1001 );
acc =gsl_interp_accel_alloc ();
gsl_spline_init( spline , x , y , 1001 );
for(int p=0;p<1001;p++) {
double evaly = gsl_spline_eval( spline , x[p] , acc );
if (evaly != y[p]) {
cout << "Point:" << p << ":" << x[p] << "," <<
y[p] << ","<< evaly << '\n';
}
}
}//end of main
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