Function.cc

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/* 
 * LSST Data Management System
 * Copyright 2008, 2009, 2010 LSST Corporation.
 * 
 * This product includes software developed by the
 * LSST Project (http://www.lsst.org/).
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program 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 General Public License for more details.
 * 
 * You should have received a copy of the LSST License Statement and 
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 * see <http://www.lsstcorp.org/LegalNotices/>.
 */
 
#include "lsst/afw/math/FunctionLibrary.h"

namespace afwMath = lsst::afw::math;

template<typename ReturnT>
std::vector<double> afwMath::PolynomialFunction2<ReturnT>::getDFuncDParameters(double x, double y) const {
    std::vector<double> coeffs(this->getNParameters());

    //
    // Go through params order by order, evaluating x^r y^s;  we do this by first evaluating
    // y^s for a complete order, then going through again multiplying by x^r
    //
    int i0 = 0;                         // starting index for this order's coefficients
    for (int order = 0; order <= this->_order; ++order) {
        coeffs[i0] = 1;
        double zn = y;                  // y^s
        for (int i = 1; i <= order; ++i) {
            coeffs[i0 + i] = zn;
            zn *= y;
        }

        zn = x;                         // x^r
        for (int i = order - 1; i >= 0; --i) {
            coeffs[i0 + i] *= zn;
            zn *= x;
        }


        i0 += order + 1;
    }

    assert (i0 == static_cast<int>(coeffs.size()));

    return coeffs;
}

/************************************************************************************************************/
#define INSTANTIATE(TYPE) \
    template std::vector<double> \
    afwMath::PolynomialFunction2<TYPE>::getDFuncDParameters(double x, double y) const

INSTANTIATE(double);
INSTANTIATE(float);