/**
* 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;
}
/**
* Return the wavelength range of the output histogram.
* @param detectorWS [in] :: the input workspace
* @param indices [in] :: the workspace indices of foreground histograms
* @param refAngles [in] :: the reference angles
* @return :: the minimum and maximum virtual wavelengths
*/
ReflectometrySumInQ::MinMax ReflectometrySumInQ::findWavelengthMinMax(
const API::MatrixWorkspace &detectorWS,
const Indexing::SpectrumIndexSet &indices, const Angles &refAngles) {
const API::SpectrumInfo &spectrumInfo = detectorWS.spectrumInfo();
// Get the new max and min X values of the projected (virtual) lambda range
const bool includePartialBins = getProperty(Prop::PARTIAL_BINS);
// Find minimum and maximum 2thetas and the corresponding indices.
// It cannot be assumed that 2theta increases with indices, check for example
// D17 at ILL
MinMax inputLambdaRange;
MinMax inputTwoThetaRange;
for (const auto i : indices) {
const auto twoThetas = twoThetaWidth(i, spectrumInfo);
inputTwoThetaRange.testAndSetMin(includePartialBins ? twoThetas.min
: twoThetas.max);
inputTwoThetaRange.testAndSetMax(includePartialBins ? twoThetas.max
: twoThetas.min);
const auto &edges = detectorWS.binEdges(i);
for (size_t xIndex = 0; xIndex < edges.size(); ++xIndex) {
// It is common for the wavelength to have negative values at ILL.
const auto x = edges[xIndex + (includePartialBins ? 0 : 1)];
if (x > 0.) {
inputLambdaRange.testAndSet(x);
break;
}
}
if (includePartialBins) {
inputLambdaRange.testAndSet(edges.back());
} else {
inputLambdaRange.testAndSet(edges[edges.size() - 2]);
}
}
MinMax outputLambdaRange;
outputLambdaRange.min = projectToReference(inputLambdaRange.min,
inputTwoThetaRange.max, refAngles);
outputLambdaRange.max = projectToReference(inputLambdaRange.max,
inputTwoThetaRange.min, refAngles);
if (outputLambdaRange.min > outputLambdaRange.max) {
throw std::runtime_error(
"Error projecting lambda range to reference line; projected range (" +
std::to_string(outputLambdaRange.min) + "," +
std::to_string(outputLambdaRange.max) + ") is negative.");
}
return outputLambdaRange;
}
/**
* 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;
}