108 lines
3.1 KiB
C++
108 lines
3.1 KiB
C++
/*
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Copyright 2009, 2010, 2013 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_INCLUDED
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#define OPM_LINEARINTERPOLATION_HEADER_INCLUDED
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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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inline int tableIndex(const std::vector<double>& table, double x)
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{
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// Returns an index in an ordered table such that x is between
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// table[j] and table[j+1]. If x is out of range, first or last
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// interval is returned; Binary search.
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int n = table.size() - 1;
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if (n < 2) {
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return 0;
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}
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int jl = 0;
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int ju = n;
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bool ascend = (table[n] > table[0]);
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while (ju - jl > 1) {
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int jm = (ju + jl)/2; // Compute a midpoint
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if ( (x >= table[jm]) == ascend) {
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jl = jm; // Replace lower limit
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} else {
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ju = jm; // Replace upper limit
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}
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}
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return jl;
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}
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inline double linearInterpolationDerivative(const std::vector<double>& xv,
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const std::vector<double>& yv, double x)
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{
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// Extrapolates if x is outside xv
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int ix1 = tableIndex(xv, x);
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int ix2 = ix1 + 1;
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return (yv[ix2] - yv[ix1])/(xv[ix2] - xv[ix1]);
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}
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inline double linearInterpolation(const std::vector<double>& xv,
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const std::vector<double>& yv, double x)
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{
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// Extrapolates if x is outside xv
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int ix1 = tableIndex(xv, x);
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int ix2 = ix1 + 1;
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return (yv[ix2] - yv[ix1])/(xv[ix2] - xv[ix1])*(x - xv[ix1]) + yv[ix1];
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}
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inline double linearInterpolationNoExtrapolation(const std::vector<double>& xv,
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const std::vector<double>& yv, double x)
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{
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// Return end values if x is outside xv
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if (x < xv.front()) {
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return yv.front();
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}
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if (x > xv.back()) {
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return yv.back();
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}
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int ix1 = tableIndex(xv, x);
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int ix2 = ix1 + 1;
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return (yv[ix2] - yv[ix1])/(xv[ix2] - xv[ix1])*(x - xv[ix1]) + yv[ix1];
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}
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inline double linearInterpolation(const std::vector<double>& xv,
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const std::vector<double>& yv,
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double x, int& ix1)
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{
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// Extrapolates if x is outside xv
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ix1 = tableIndex(xv, x);
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int ix2 = ix1 + 1;
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return (yv[ix2] - yv[ix1])/(xv[ix2] - xv[ix1])*(x - xv[ix1]) + yv[ix1];
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}
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} // namespace Opm
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#endif // OPM_LINEARINTERPOLATION_HEADER_INCLUDED
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