/**
* Construct an "empty" output workspace in virtual-lambda for summation in Q.
*
* @param detectorWS [in] :: the input workspace
* @param indices [in] :: the workspace indices of the foreground histograms
* @param refAngles [in] :: the reference angles
* @return :: a 1D workspace where y values are all zero
*/
API::MatrixWorkspace_sptr ReflectometrySumInQ::constructIvsLamWS(
const API::MatrixWorkspace &detectorWS,
const Indexing::SpectrumIndexSet &indices, const Angles &refAngles) {
// Calculate the number of bins based on the min/max wavelength, using
// the same bin width as the input workspace
const auto &edges = detectorWS.binEdges(refAngles.referenceWSIndex);
const double binWidth =
(edges.back() - edges.front()) / static_cast<double>(edges.size());
const auto wavelengthRange =
findWavelengthMinMax(detectorWS, indices, refAngles);
if (std::abs(wavelengthRange.max - wavelengthRange.min) < binWidth) {
throw std::runtime_error("Given wavelength range too small.");
}
const int numBins = static_cast<int>(
std::ceil((wavelengthRange.max - wavelengthRange.min) / binWidth));
// Construct the histogram with these X values. Y and E values are zero.
const HistogramData::BinEdges bins(
numBins + 1,
HistogramData::LinearGenerator(wavelengthRange.min, binWidth));
const HistogramData::Counts counts(numBins, 0.);
const HistogramData::Histogram modelHistogram(std::move(bins),
std::move(counts));
// Create the output workspace
API::MatrixWorkspace_sptr outputWS =
DataObjects::create<DataObjects::Workspace2D>(detectorWS, 1,
std::move(modelHistogram));
// Set the detector IDs and specturm number from the twoThetaR detector.
const auto &thetaSpec = detectorWS.getSpectrum(refAngles.referenceWSIndex);
auto &outSpec = outputWS->getSpectrum(0);
outSpec.clearDetectorIDs();
outSpec.addDetectorIDs(thetaSpec.getDetectorIDs());
outSpec.setSpectrumNo(thetaSpec.getSpectrumNo());
return outputWS;
}
