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101 lines
3.2 KiB
C++
101 lines
3.2 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2021 Jon Beniston, M7RCE <jon@beniston.com> //
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// //
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// This program 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 as version 3 of the License, or //
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// (at your option) any later version. //
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// //
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// This program 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 V3 for more details. //
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// //
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// You should have received a copy of the GNU General Public License //
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// along with this program. If not, see <http://www.gnu.org/licenses/>. //
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///////////////////////////////////////////////////////////////////////////////////
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#ifndef INCLUDE_INTERPOLATION_H
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#define INCLUDE_INTERPOLATION_H
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#include "export.h"
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#include <iterator>
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class SDRBASE_API Interpolation {
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public:
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// Linear interpolation/extrapolation
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// Assumes x is sorted in increasing order
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template<class Iter, class T>
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static T linear(Iter xBegin, Iter xEnd, Iter yBegin, T x)
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{
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// Find first point in x that target is bigger than
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int i = 0;
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while (xBegin != xEnd)
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{
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if (x < *xBegin) {
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break;
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}
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++xBegin;
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i++;
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}
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T x0, x1, y0, y1;
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if (i == 0) {
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// Extrapolate left
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x0 = *xBegin;
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++xBegin;
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x1 = *xBegin;
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y0 = *yBegin;
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++yBegin;
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y1 = *yBegin;
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return extrapolate(x0, y0, x1, y1, x);
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} else if (xBegin > xEnd) {
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// Extrapolate right
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Iter xCur = xBegin;
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std::advance(xCur, i - 2);
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x0 = *xCur;
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++xCur;
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x1 = *xCur;
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Iter yCur = yBegin;
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std::advance(yCur, i - 2);
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y0 = *yCur;
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++yCur;
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y1 = *yCur;
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return extrapolate(x0, y0, x1, y1, x);
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} else {
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// Interpolate
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x1 = *xBegin;
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--xBegin;
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x0 = *xBegin;
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Iter yCur = yBegin;
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std::advance(yCur, i - 1);
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y0 = *yCur;
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++yCur;
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y1 = *yCur;
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return interpolate(x0, y0, x1, y1, x);
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}
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}
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// Linear extrapolation
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template<class T>
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static T extrapolate(T x0, T y0, T x1, T y1, T x)
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{
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return y0 + ((x-x0)/(x1-x0)) * (y1-y0);
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}
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// Linear interpolation
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template<class T>
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static T interpolate(T x0, T y0, T x1, T y1, T x)
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{
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return (y0*(x1-x) + y1*(x-x0)) / (x1-x0);
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}
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};
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#endif // INCLUDE_INTERPOLATION_H
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