128 lines
3.4 KiB
C++
128 lines
3.4 KiB
C++
//===========================================================================
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//
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// File: linearInterpolation.hpp
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//
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// Created: Tue Sep 9 12:49:39 2008
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//
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// Author(s): Atgeirr F Rasmussen <atgeirr@sintef.no>
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//
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// $Date$
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//
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// $Revision$
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//
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//===========================================================================
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/*
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Copyright 2009, 2010 SINTEF ICT, Applied Mathematics.
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Copyright 2009, 2010 Statoil ASA.
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This file is part of the Open Porous Media project (OPM).
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OPM is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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OPM is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with OPM. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef OPM_LINEARINTERPOLATION_HEADER
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#define OPM_LINEARINTERPOLATION_HEADER
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#include <vector>
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#include <algorithm>
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namespace Opm
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{
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/** Linear interpolation.
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* Given an increasing vector xv of parameter values and
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* a vector yv of point values of the same size,
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* the function returns ...
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*/
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template <typename T>
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T linearInterpolation(const std::vector<double>& xv,
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const std::vector<T>& yv,
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double x)
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{
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std::vector<double>::const_iterator lb = std::lower_bound(xv.begin(), xv.end(), x);
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int lb_ix = lb - xv.begin();
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if (lb_ix == 0) {
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return yv[0];
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} else if (lb_ix == int(xv.size())) {
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return yv.back();
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} else {
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double w = (x - xv[lb_ix - 1])/(xv[lb_ix] - xv[lb_ix - 1]);
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return (1.0 - w)*yv[lb_ix - 1] + w*yv[lb_ix];
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}
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}
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/// @brief
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/// @todo Doc me!
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/// @tparam
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/// @param
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/// @return
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template <typename T>
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T linearInterpolationDerivative(const std::vector<double>& xv,
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const std::vector<T>& yv,
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double x)
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{
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std::vector<double>::const_iterator lb = std::lower_bound(xv.begin(), xv.end(), x);
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int lb_ix = lb - xv.begin();
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if (lb_ix == 0) {
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return 0.;
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} else if (lb_ix == int(xv.size())) {
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return 0.;
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} else {
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return (yv[lb_ix] - yv[lb_ix - 1])/(xv[lb_ix] - xv[lb_ix - 1]);
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}
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}
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template <typename T>
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T linearInterpolationDerivativeExtrap(const std::vector<double>& xv,
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const std::vector<T>& yv,
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double x)
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{
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std::vector<double>::const_iterator lb = std::lower_bound(xv.begin(), xv.end(), x);
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int lb_ix = lb - xv.begin();
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int nend = int(xv.size());
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if (lb_ix == 0) {
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return (yv[1]-yv[0])/(xv[1]-xv[0]);
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} else if (lb_ix == int(xv.size())) {
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return (yv[nend-1]-yv[nend-2])/(xv[nend-1]-xv[nend-2]);
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} else {
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return (yv[lb_ix] - yv[lb_ix - 1])/(xv[lb_ix] - xv[lb_ix - 1]);
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}
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}
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template <typename T>
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T linearInterpolationExtrap(const std::vector<double>& xv,
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const std::vector<T>& yv,
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double x)
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{
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std::vector<double>::const_iterator lb = std::lower_bound(xv.begin(), xv.end(), x);
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int lb_ix = lb - xv.begin();
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if (lb_ix == 0) {
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lb_ix=1;
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} else if (lb_ix == int(xv.size())){
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lb_ix = int(xv.size())-1;
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}
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double w = (x - xv[lb_ix - 1])/(xv[lb_ix] - xv[lb_ix - 1]);
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return (1.0 - w)*yv[lb_ix - 1] + w*yv[lb_ix];
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}
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} // namespace Opm
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#endif // OPM_LINEARINTERPOLATION_HEADER
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