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DensityScan1D.cc
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DensityScan1D.cc
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#include "npstat/stat/DensityScan1D.hh"
#include "npstat/nm/GaussLegendreQuadrature.hh"
namespace npstat {
DensityScan1D::DensityScan1D(const AbsDistribution1D& fcn,
const double normfactor,
const unsigned long nbins,
const double xmin, const double xmax,
const unsigned nIntegrationPoints)
: fcn_(fcn),
norm_(normfactor),
xmin_(xmin),
bw_((xmax-xmin)/nbins),
nPoints_(nIntegrationPoints)
{
if (!nbins) throw std::invalid_argument(
"In npstat::DensityScan1D constructor: "
"number of bins must be positive");
if (nPoints_ > 1U)
{
GaussLegendreQuadrature q(nPoints_);
if (!q.npoints()) throw std::invalid_argument(
"In npstat::DensityScan1D constructor: this number "
"of integration points per bin is not supported by "
"npstat::GaussLegendreQuadrature");
weights_.resize(nPoints_/2U);
a_.resize(nPoints_/2U);
q.getWeights(&weights_[0], weights_.size());
q.getAbscissae(&a_[0], a_.size());
}
}
double DensityScan1D::operator()(const unsigned* index, unsigned len) const
{
if (len != 1U) throw std::invalid_argument(
"In npstat::DensityScan1D::operator(): "
"incompatible dimensionality of the input index");
assert(index);
if (nPoints_)
{
const double midpoint = xmin_ + (*index + 0.5)*bw_;
if (nPoints_ == 1U)
return fcn_.density(midpoint)*norm_;
else
{
const long double *w = &weights_[0];
const long double *ab = &a_[0];
const unsigned halfpoints = nPoints_/2U;
long double sum = 0.0L;
for (unsigned i=0; i<halfpoints; ++i)
{
const double delta = bw_/2.0*static_cast<double>(ab[i]);
sum += w[i]*fcn_.density(midpoint - delta);
sum += w[i]*fcn_.density(midpoint + delta);
}
return norm_*static_cast<double>(sum/2.0L);
}
}
else
{
const double leftedge = xmin_ + *index*bw_;
const double rightedge = leftedge + bw_;
return norm_*(fcn_.cdf(rightedge) - fcn_.cdf(leftedge))/bw_;
}
}
}

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