/** Calculates Sn as estimator of scale for given vector
*
* This method implements a naive calculation of Sn, as defined by Rousseeuw
*and Croux (http://dx.doi.org/10.2307%2F2291267).
* In contrast to standard deviation, this is more robust towards outliers.
*
* @param begin :: Beginning of vector.
* @param end :: End of vector.
* @return Sn of supplied data.
*/
double PoldiPeakSearch::getSn(MantidVec::const_iterator begin,
MantidVec::const_iterator end) const {
size_t numberOfPoints = std::distance(begin, end);
MantidVec absoluteDifferenceMedians(numberOfPoints);
PARALLEL_FOR_NO_WSP_CHECK()
for (int i = 0; i < static_cast<int>(numberOfPoints); ++i) {
double currentValue = *(begin + i);
MantidVec temp;
temp.reserve(numberOfPoints - 1);
for (int j = 0; j < static_cast<int>(numberOfPoints); ++j) {
if (j != i) {
temp.push_back(fabs(*(begin + j) - currentValue));
}
}
std::sort(temp.begin(), temp.end());
absoluteDifferenceMedians[i] =
getMedianFromSortedVector(temp.begin(), temp.end());
}
std::sort(absoluteDifferenceMedians.begin(), absoluteDifferenceMedians.end());
return 1.1926 * getMedianFromSortedVector(absoluteDifferenceMedians.begin(),
absoluteDifferenceMedians.end());
}
/** Retrieves a vector with all counts that belong to the background
*
* In this method, a vector is assembled which contains all count data that is
*considered to be background.
* Whether a point is considered background depends on its distance to the
*given peak positions.
*
* @param peakPositions :: Peak positions.
* @param correlationCounts :: Vector with the complete correlation spectrum.
* @return Vector only with counts that belong to the background.
*/
MantidVec PoldiPeakSearch::getBackground(
std::list<MantidVec::const_iterator> peakPositions,
const MantidVec &correlationCounts) const {
size_t backgroundPoints =
getNumberOfBackgroundPoints(peakPositions, correlationCounts);
MantidVec background;
background.reserve(backgroundPoints);
for (MantidVec::const_iterator point = correlationCounts.begin() + 1;
point != correlationCounts.end() - 1; ++point) {
if (distanceToPeaksGreaterThanMinimum(peakPositions, point)) {
background.push_back(*point);
}
}
return background;
}