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67 lines
2.0 KiB
C++
67 lines
2.0 KiB
C++
/////////////////////////////////////////////////////////////////////////////////
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//
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// Copyright (C) 2020 Equinor ASA
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//
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// ResInsight 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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//
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// ResInsight is distributed in the hope that it will be useful, but WITHOUT ANY
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE.
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//
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// See the GNU General Public License at <http://www.gnu.org/licenses/gpl.html>
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// for more details.
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//
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/////////////////////////////////////////////////////////////////////////////////
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#include "RiaInterpolationTools.h"
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#include <cassert>
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#include <limits>
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//--------------------------------------------------------------------------------------------------
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///
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//--------------------------------------------------------------------------------------------------
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double RiaInterpolationTools::linear( const std::vector<double>& x, const std::vector<double>& y, double value )
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{
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assert( x.size() == y.size() );
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// Handle cases with only one data point.
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if ( x.size() == 1 )
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{
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return std::numeric_limits<double>::infinity();
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}
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// Find the lower boundary
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bool found = false;
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int lowerIndex = 0;
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for ( int i = 0; i < static_cast<int>( x.size() - 1 ); i++ )
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{
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if ( x[i] < value && x[i + 1] > value )
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{
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lowerIndex = i;
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found = true;
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}
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}
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// Value is outside of the defined range
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if ( !found )
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{
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return std::numeric_limits<double>::infinity();
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}
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int upperIndex = lowerIndex + 1;
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double lowerX = x[lowerIndex];
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double lowerY = y[lowerIndex];
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double upperX = x[upperIndex];
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double upperY = y[upperIndex];
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double deltaY = upperY - lowerY;
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double deltaX = upperX - lowerX;
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return lowerY + ( ( value - lowerX ) / deltaX ) * deltaY;
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}
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