ESPResSo
Extensible Simulation Package for Research on Soft Matter Systems
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linear_interpolation.hpp
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1/*
2 * Copyright (C) 2010-2022 The ESPResSo project
3 *
4 * This file is part of ESPResSo.
5 *
6 * ESPResSo is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, either version 3 of the License, or
9 * (at your option) any later version.
10 *
11 * ESPResSo is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 */
19
20#pragma once
21
22#include <cassert>
23#include <cstddef>
24
25namespace Utils {
26/** Linear interpolation between two data points.
27 * @param[in] table Tabulated values, equally-spaced along the x-axis
28 * @param[in] hi Distance on the x-axis between tabulated values
29 * @param[in] offset Position on the x-axis of the first tabulated value
30 * @param[in] x Position on the x-axis at which to interpolate the value
31 * @return Interpolated value on the y-axis at @p x.
32 */
33template <typename T, typename Container>
34T linear_interpolation(Container const &table, T hi, T offset, T x) {
35 auto const dind = (x - offset) * hi;
36 auto const ind = static_cast<int>(dind);
37 assert(ind <= dind);
38 assert((ind >= 0) and (static_cast<std::size_t>(ind) < table.size()));
39 auto const dx = dind - static_cast<T>(ind);
40 auto const uind = static_cast<unsigned int>(ind);
41
42 /* linear interpolation between data points */
43 return table[uind] * (T{1} - dx) + table[uind + 1] * dx;
44}
45} // namespace Utils
T linear_interpolation(Container const &table, T hi, T offset, T x)
Linear interpolation between two data points.