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// 2008 © Václav Šmilauer <eudoxos@arcig.cz>
#pragma once
#include <lib/base/Math.hpp>
#include <cassert>
#include <iostream>
#include <vector>
/* Linear interpolation function suitable only for sequential interpolation.
*
* Template parameter T must support: addition, subtraction, scalar multiplication.
*
* @param t "time" at which the interpolated variable should be evaluated.
* @param tt "time" points at which values are given; must be increasing.
* @param values values at "time" points specified by tt
* @param pos holds lookup state
*
* @return value at "time" t; out of range: t<t0 → value(t0), t>t_last → value(t_last)
*/
template <typename T, typename timeT> T linearInterpolate(const ::yade::Real t, const std::vector<timeT>& tt, const std::vector<T>& values, size_t& pos)
{
assert(tt.size() == values.size());
if (t <= tt[0]) {
pos = 0;
return values[0];
}
if (t >= *tt.rbegin()) {
pos = tt.size() - 2;
return *values.rbegin();
}
pos = std::min(pos, tt.size() - 2);
while ((tt[pos] > t) || (tt[pos + 1] < t)) {
assert(tt[pos] < tt[pos + 1]);
if (tt[pos] > t) pos--;
else
pos++;
}
const ::yade::Real &t0 = tt[pos], t1 = tt[pos + 1];
const T & v0 = values[pos], v1 = values[pos + 1];
return v0 + (v1 - v0) * ((t - t0) / (t1 - t0));
}
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