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TabFunction: Implemented quadratic interpolation

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Matt Spraggs 2015-11-10 12:23:29 +00:00
parent ff49304137
commit 64372eb9dc
2 changed files with 51 additions and 14 deletions
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63
lib/TabFunction.cpp
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@ -72,14 +72,14 @@ double TabFunction::operator()(const double *arg) const
+ strFrom(value_.rbegin()->first) + "])");
}
auto i = value_.equal_range(x);
auto low = (x == i.first->first) ? i.first : prev(i.first);
auto high = i.second;
switch (interpType_) {
case InterpType::LINEAR: {
double x_a, x_b, y_a, y_b;
auto i = value_.equal_range(x);
auto low = (x == i.first->first) ? i.first : prev(i.first);
auto high = i.second;
x_a = low->first;
x_b = high->first;
y_a = low->second;
@ -88,18 +88,37 @@ double TabFunction::operator()(const double *arg) const
break;
}
case InterpType::NEAREST: {
auto it = value_.equal_range(x);
auto lower = (x == it.first->first) ? it.first : prev(it.first);
auto upper = it.second;
if (fabs(upper->first - x) < fabs(lower->first - x)) {
result = upper->second;
}
else {
result = lower->second;
}
result = nearest(x)->second;
break;
}
case InterpType::QUADRATIC: {
double xs[3], ys[3], as[3];
auto it = nearest(x);
if (it == value_.begin()) {
it = next(it);
}
else if (it == value_.end()) {
it = prev(it);
}
xs[0] = prev(it)->first;
ys[0] = prev(it)->second;
xs[1] = it->first;
ys[1] = it->second;
xs[2] = next(it)->first;
ys[2] = next(it)->second;
as[0]
= (x - xs[1]) / (xs[0] - xs[1])
* (x - xs[2]) / (xs[0] - xs[2]);
as[1]
= (x - xs[0]) / (xs[1] - xs[0])
* (x - xs[2]) / (xs[1] - xs[2]);
as[2]
= (x - xs[0]) / (xs[2] - xs[0])
* (x - xs[1]) / (xs[2] - xs[1]);
result = as[0] * ys[0] + as[1] * ys[1] + as[2] * ys[2];
break;
}
case InterpType::QUADRATIC:
default:
int intType = static_cast<int>(interpType_);
LATAN_ERROR(Implementation, "unsupported interpolation type in "
@ -140,3 +159,19 @@ DoubleFunction Latan::interpolate(const XYStatData &data, const Index i,
{
return TabFunction(data, i, j, interpType).makeFunction();
}
map<double, double>::const_iterator TabFunction::nearest(const double x) const
{
map<double, double>::const_iterator ret;
auto i = value_.equal_range(x);
auto low = (x == i.first->first) ? i.first : prev(i.first);
auto high = i.second;
if (fabs(high->first - x) < fabs(low->first - x)) {
ret = high;
}
else {
ret = low;
}
return ret;
};

2
lib/TabFunction.hpp
View File

@ -59,6 +59,8 @@ public:
// factory
virtual DoubleFunction makeFunction(const bool makeHardCopy = true) const;
private:
std::map<double, double>::const_iterator nearest(const double x) const;
std::map<double, double> value_;
InterpType interpType_;
};