/**
* Sum counts from the input workspace in lambda along lines of constant Q by
* projecting to "virtual lambda" at a reference angle.
*
* @param detectorWS [in] :: the input workspace in wavelength
* @param indices [in] :: an index set defining the foreground histograms
* @return :: the single histogram output workspace in wavelength
*/
API::MatrixWorkspace_sptr
ReflectometrySumInQ::sumInQ(const API::MatrixWorkspace &detectorWS,
const Indexing::SpectrumIndexSet &indices) {
const auto spectrumInfo = detectorWS.spectrumInfo();
const auto refAngles = referenceAngles(spectrumInfo);
// Construct the output workspace in virtual lambda
API::MatrixWorkspace_sptr IvsLam =
constructIvsLamWS(detectorWS, indices, refAngles);
auto &outputE = IvsLam->dataE(0);
// Loop through each spectrum in the detector group
for (auto spIdx : indices) {
if (spectrumInfo.isMasked(spIdx) || spectrumInfo.isMonitor(spIdx)) {
continue;
}
// Get the size of this detector in twoTheta
const auto twoThetaRange = twoThetaWidth(spIdx, spectrumInfo);
// Check X length is Y length + 1
const auto inputBinEdges = detectorWS.binEdges(spIdx);
const auto inputCounts = detectorWS.counts(spIdx);
const auto inputStdDevs = detectorWS.countStandardDeviations(spIdx);
// Create a vector for the projected errors for this spectrum.
// (Output Y values can simply be accumulated directly into the output
// workspace, but for error values we need to create a separate error
// vector for the projected errors from each input spectrum and then
// do an overall sum in quadrature.)
std::vector<double> projectedE(outputE.size(), 0.0);
// Process each value in the spectrum
const int ySize = static_cast<int>(inputCounts.size());
for (int inputIdx = 0; inputIdx < ySize; ++inputIdx) {
// Do the summation in Q
processValue(inputIdx, twoThetaRange, refAngles, inputBinEdges,
inputCounts, inputStdDevs, *IvsLam, projectedE);
}
// Sum errors in quadrature
const int eSize = static_cast<int>(outputE.size());
for (int outIdx = 0; outIdx < eSize; ++outIdx) {
outputE[outIdx] += projectedE[outIdx] * projectedE[outIdx];
}
}
// Take the square root of all the accumulated squared errors for this
// detector group. Assumes Gaussian errors
double (*rs)(double) = std::sqrt;
std::transform(outputE.begin(), outputE.end(), outputE.begin(), rs);
return IvsLam;
}
