LSSTApplications  20.0.0
LSSTDataManagementBasePackage
PolynomialFunction1d.cc
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1 // -*- LSST-C++ -*-
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22 
23 #include <vector>
24 
28 
29 
30 namespace lsst { namespace geom { namespace polynomials {
31 
33  auto const & basis = f.getBasis();
34  std::vector<SafeSum<double>> sums(basis.size());
35  double const s = basis.getScaling().getScale();
36  double const v = basis.getScaling().getShift();
37  double sn = 1; // s^n
38  BinomialMatrix binomial(basis.getNested().getOrder());
39  for (std::size_t n = 0; n < basis.size(); ++n, sn *= s) {
40  double vk = 1; // v^k
41  for (std::size_t k = 0; k <= n; ++k, vk *= v) {
42  sums[n - k] += sn*binomial(n, k)*f[n]*vk;
43  }
44  }
45  Eigen::VectorXd result = Eigen::VectorXd::Zero(basis.size());
46  for (std::size_t n = 0; n < basis.size(); ++n) {
47  result[n] = static_cast<double>(sums[n]);
48  }
49  return makeFunction1d(basis.getNested(), result);
50 }
51 
52 }}} // namespace lsst::geom::polynomials
lsst::geom::polynomials::BinomialMatrix
A class that computes binomial coefficients up to a certain power.
Definition: BinomialMatrix.h:45
SafeSum.h
std::vector
STL class.
PolynomialFunction1d.h
lsst::geom::polynomials::simplified
PolynomialFunction1d simplified(ScaledPolynomialFunction1d const &f)
Calculate the standard polynomial function that is equivalent to a scaled standard polynomial functio...
Definition: PolynomialFunction1d.cc:32
basis
table::Key< table::Array< double > > basis
Definition: PsfexPsf.cc:361
lsst::geom::polynomials::Function1d
A 1-d function defined by a series expansion and its coefficients.
Definition: Function1d.h:42
result
py::object result
Definition: _schema.cc:429
lsst
A base class for image defects.
Definition: imageAlgorithm.dox:1
lsst::geom
Definition: geomOperators.dox:4
std::size_t
lsst::geom::polynomials::Function1d::getBasis
Basis const & getBasis() const
Return the associated Basis1d object.
Definition: Function1d.h:98
lsst::geom::polynomials::makeFunction1d
Function1d< Basis > makeFunction1d(Basis const &basis, Eigen::VectorXd const &coefficients)
Create a Function1d of the appropriate type from a Basis1d and an Eigen object containing coefficient...
Definition: Function1d.h:144
BinomialMatrix.h