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//# Chebyshev.cc a function class that defines a Chebyshev polynomial
//# Copyright (C) 2000,2001,2002
//# Associated Universities, Inc. Washington DC, USA.
//#
//# This library is free software; you can redistribute it and/or modify it
//# under the terms of the GNU Library General Public License as published by
//# the Free Software Foundation; either version 2 of the License, or (at your
//# option) any later version.
//#
//# This library is distributed in the hope that it will be useful, but WITHOUT
//# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
//# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
//# License for more details.
//#
//# You should have received a copy of the GNU Library General Public License
//# along with this library; if not, write to the Free Software Foundation,
//# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
//#
//# Correspondence concerning AIPS++ should be addressed as follows:
//# Internet email: casa-feedback@nrao.edu.
//# Postal address: AIPS++ Project Office
//# National Radio Astronomy Observatory
//# 520 Edgemont Road
//# Charlottesville, VA 22903-2475 USA
//#
//#! ========================================================================
#ifndef SCIMATH_CHEBYSHEV_TCC
#define SCIMATH_CHEBYSHEV_TCC
//# Includes
#include <casacore/scimath/Functionals/Chebyshev.h>
namespace casacore { //# NAMESPACE CASACORE - BEGIN
//# Constructors
//# Operators
template <class T>
T Chebyshev<T>::eval(const typename FunctionTraits<T>::ArgType *x) const {
T xp = x[0];
// handle out-of-interval values
if (xp < this->minx_p || xp > this->maxx_p) {
switch (this->mode_p) {
case ChebyshevEnums::CONSTANT:
return this->def_p;
case ChebyshevEnums::ZEROTH:
return this->param_p[0];
case ChebyshevEnums::CYCLIC: {
T period = (this->maxx_p-this->minx_p);
while (xp < this->minx_p) xp += period;
while (xp > this->maxx_p) xp -= period;
}
break;
case ChebyshevEnums::EDGE: {
T tmp(0);
if (xp<this->minx_p) {
for (uInt i=0; i<this->nparameters(); i+=2) tmp += this->param_p[i];
for (uInt i=1; i<this->nparameters(); i+=2) tmp -= this->param_p[i];
} else {
for (uInt i=0; i<this->nparameters(); ++i) tmp += this->param_p[i];
}
return tmp;
}
break;
default:
break;
}
}
T yi1=T(0);
T yi2=T(0);
T tmp;
// map Chebeshev range [this->minx_p, this->maxx_p] into [-1, 1]
xp = (T(2)*xp-this->minx_p-this->maxx_p)/(this->maxx_p-this->minx_p);
// evaluate using Clenshaw recursion relation
for (Int i=this->nparameters()-1; i>0; i--) {
tmp = T(2)*xp*yi1 - yi2 + this->param_p[i];
yi2 = yi1;
yi1 = tmp;
}
return xp*yi1 - yi2 + this->param_p[0];
}
template <class T>
Chebyshev<T> Chebyshev<T>::derivative() const {
Vector<T> ce(this->nparameters());
ce = this->parameters().getParameters();
this->derivativeCoeffs(ce, this->minx_p, this->maxx_p);
return Chebyshev<T>(ce, this->minx_p, this->maxx_p, this->mode_p, T(0));
}
//# Member functions
} //# NAMESPACE CASACORE - END
#endif
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