double PiecewiseLinearInterpolation::getValue(double pnt_to_interpolate) const
{
// search interval that has the point inside
std::size_t interval_idx(std::numeric_limits<std::size_t>::max());
if (pnt_to_interpolate <= _supp_pnts.front()) {
interval_idx = 0;
} else {
if (_supp_pnts.back() <= pnt_to_interpolate) {
interval_idx = _supp_pnts.size() - 2;
} else {
auto const& it(std::lower_bound(_supp_pnts.begin(), _supp_pnts.end(), pnt_to_interpolate));
interval_idx = std::distance(_supp_pnts.begin(), it) - 1;
}
}
if (pnt_to_interpolate > _supp_pnts.back()){
return _values_at_supp_pnts[_supp_pnts.size() - 1];
}
if (pnt_to_interpolate < _supp_pnts.front()){
return _values_at_supp_pnts[0];
}
// compute linear interpolation polynom: y = m * (x - support[i]) + value[i]
const double m((_values_at_supp_pnts[interval_idx + 1] - _values_at_supp_pnts[interval_idx])
/ (_supp_pnts[interval_idx + 1] - _supp_pnts[interval_idx]));
return m * (pnt_to_interpolate - _supp_pnts[interval_idx]) + _values_at_supp_pnts[interval_idx];
}
double PiecewiseLinearInterpolation::getValue(double pnt_to_interpolate)
{
// search interval that has the point inside
size_t interval_idx(std::numeric_limits<size_t>::max());
for (size_t k(1); k < _supporting_points.size() && interval_idx == std::numeric_limits<size_t>::max(); k++)
if (_supporting_points[k - 1] <= pnt_to_interpolate && pnt_to_interpolate <= _supporting_points[k])
interval_idx = k - 1;
// compute linear interpolation polynom: y = m * x + n
long double m((_values_at_supp_pnts[interval_idx + 1] - _values_at_supp_pnts[interval_idx])
/ (_supporting_points[interval_idx + 1] - _supporting_points[interval_idx]));
// double m ((_values_at_supp_pnts[interval_idx] - _values_at_supp_pnts[interval_idx+1]) /
//(_supporting_points[interval_idx] - _supporting_points[interval_idx+1]));
// double n (_values_at_supp_pnts[interval_idx+1] - m * _supporting_points[interval_idx+1]);
long double n(_values_at_supp_pnts[interval_idx] - m * _supporting_points[interval_idx]);
return m * pnt_to_interpolate + n;
}
double PiecewiseLinearInterpolation::GetCurveDerivative(double pnt_to_interpolate) const
{
std::size_t interval_max(std::numeric_limits<std::size_t>::max());//anz
std::size_t interval_idx(std::numeric_limits<std::size_t>::max());//anz
interval_max = _supp_pnts.size();
if (pnt_to_interpolate <= _supp_pnts.front()) {
interval_idx = 0;
}
else {
if (_supp_pnts.back() <= pnt_to_interpolate) {
interval_idx = _supp_pnts.size() - 2;
}
else {
auto const& it(std::lower_bound(_supp_pnts.begin(), _supp_pnts.end(), pnt_to_interpolate));
interval_idx = std::distance(_supp_pnts.begin(), it) - 1;
}
}
double sw = getValue(pnt_to_interpolate);
if (sw < _values_at_supp_pnts[interval_max - 1]){
sw = _values_at_supp_pnts[interval_max - 1];
interval_idx = interval_max - 1;
}
else if (sw > _values_at_supp_pnts[0]){
sw = _values_at_supp_pnts[0];
interval_idx = 1;
}
//interval_idx = interval_max - 1 - interval_idx;
if (interval_idx > 1 && interval_idx < interval_max - 2){
double s1 = (0.5*_supp_pnts[interval_idx] - 0.5*_supp_pnts[interval_idx + 2]) / (0.5*_values_at_supp_pnts[interval_idx] - 0.5*_values_at_supp_pnts[interval_idx + 2]);
double s2 = (0.5*_supp_pnts[interval_idx-1] - 0.5*_supp_pnts[interval_idx + 1]) / (0.5*_values_at_supp_pnts[interval_idx-1] - 0.5*_values_at_supp_pnts[interval_idx + 1]);
double w = (sw - _values_at_supp_pnts[interval_idx + 1]) / (_values_at_supp_pnts[interval_idx] - _values_at_supp_pnts[interval_idx + 1]);
return (1. - w) * s1 + w * s2;
}
else{
if (std::fabs(_values_at_supp_pnts[interval_idx] - _values_at_supp_pnts[interval_idx + 1])>DBL_MIN)
return (_supp_pnts[interval_idx] - _supp_pnts[interval_idx + 1]) / (_values_at_supp_pnts[interval_idx] - _values_at_supp_pnts[interval_idx + 1]);
else
return 1 / DBL_EPSILON;
}
}
double PiecewiseLinearInterpolation::getSlope(double pnt_to_interpolate) const
{
std::size_t interval_idx(std::numeric_limits<std::size_t>::max());
//double eps = 1e-9;
if (pnt_to_interpolate <= _supp_pnts.front()) {
interval_idx = 0;
}
else {
if (_supp_pnts.back() <= pnt_to_interpolate) {
interval_idx = _supp_pnts.size() - 2;
}
else {
auto const& it(std::lower_bound(_supp_pnts.begin(), _supp_pnts.end(), pnt_to_interpolate));
interval_idx = std::distance(_supp_pnts.begin(), it) - 1;
}
}
const double m((_values_at_supp_pnts[interval_idx + 1] - _values_at_supp_pnts[interval_idx])
/ (_supp_pnts[interval_idx + 1] - _supp_pnts[interval_idx]));
//double m_test = (getValue(pnt_to_interpolate + eps) - getValue(pnt_to_interpolate - eps)) / 2 / eps;
return m;
}
