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LSST Data Management Base Package
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transforms.cc
Go to the documentation of this file.
1#include <limits>
2
4
6
7namespace lsst::gauss2d::fit {
8static const double INF = std::numeric_limits<double>::infinity();
9
10double LogitLimitedTransform::derivative(double x) const {
11 double y = (x - _limits->get_min()) / _range;
12 if (y == 1)
13 return INF;
14 else if (y == 0)
15 return -INF;
16 return (1 / y + 1 / (1 - y)) * _factor / _range;
17}
18
19double LogitLimitedTransform::forward(double x) const {
20 double min = _limits->get_min();
21 double max = _limits->get_max();
22 if (x == min)
24 else if (x == max)
26 double y = (x - min) / _range;
27 if (!(y < 1) || !(y > 0)) return nan("");
28 return log(y / (1 - y)) * _factor;
29}
30
31double LogitLimitedTransform::reverse(double x) const {
32 double y = -x * _factor;
33 // math.log(np.finfo(np.float64) = 709.782712893384
34 // things will go badly well before then
35 if (y > 709.7827) return _limits->get_min();
36 y = 1 + exp(y);
37 return _range / y + _limits->get_min();
38}
39} // namespace lsst::gauss2d::fit
double forward(double x) const override
Return the transformed value of x.
Definition transforms.cc:19
double derivative(double x) const override
Return the derivative of this tranform at the value x.
Definition transforms.cc:10
double reverse(double x) const override
Return the original value of x given a transformed value.
Definition transforms.cc:31
T infinity(T... args)