/**
* Linearly interpolate between the points in integrFlux at xValues and save the
* results in yValues.
* @param xValues :: X-values at which to interpolate
* @param integrFlux :: A workspace with the spectra to interpolate
* @param sp :: A workspace index for a spectrum in integrFlux to interpolate.
* @param yValues :: A vector to save the results.
*/
void MDNormSCD::calcIntegralsForIntersections(
const std::vector<double> &xValues, const API::MatrixWorkspace &integrFlux,
size_t sp, std::vector<double> &yValues) const {
assert(xValues.size() == yValues.size());
// the x-data from the workspace
const auto &xData = integrFlux.readX(sp);
const double xStart = xData.front();
const double xEnd = xData.back();
// the values in integrFlux are expected to be integrals of a non-negative
// function
// ie they must make a non-decreasing function
const auto &yData = integrFlux.readY(sp);
size_t spSize = yData.size();
const double yMin = 0.0;
const double yMax = yData.back();
size_t nData = xValues.size();
// all integrals below xStart must be 0
if (xValues[nData - 1] < xStart) {
std::fill(yValues.begin(), yValues.end(), yMin);
return;
}
// all integrals above xEnd must be equal tp yMax
if (xValues[0] > xEnd) {
std::fill(yValues.begin(), yValues.end(), yMax);
return;
}
size_t i = 0;
// integrals below xStart must be 0
while (i < nData - 1 && xValues[i] < xStart) {
yValues[i] = yMin;
i++;
}
size_t j = 0;
for (; i < nData; i++) {
// integrals above xEnd must be equal tp yMax
if (j >= spSize - 1) {
yValues[i] = yMax;
} else {
double xi = xValues[i];
while (j < spSize - 1 && xi > xData[j])
j++;
// if x falls onto an interpolation point return the corresponding y
if (xi == xData[j]) {
yValues[i] = yData[j];
} else if (j == spSize - 1) {
// if we get above xEnd it's yMax
yValues[i] = yMax;
} else if (j > 0) {
// interpolate between the consecutive points
double x0 = xData[j - 1];
double x1 = xData[j];
double y0 = yData[j - 1];
double y1 = yData[j];
yValues[i] = y0 + (y1 - y0) * (xi - x0) / (x1 - x0);
} else // j == 0
{
yValues[i] = yMin;
}
}
}
}
