void Linear::exec()
{
// Get the input workspace
MatrixWorkspace_const_sptr inputWorkspace = getProperty("InputWorkspace");
// Get the spectrum to fit
const int histNumber = getProperty("WorkspaceIndex");
// Check validity
if ( histNumber >= static_cast<int>(inputWorkspace->getNumberHistograms()) )
{
g_log.error() << "WorkspaceIndex set to an invalid value of " << histNumber << std::endl;
throw Exception::IndexError(histNumber,inputWorkspace->getNumberHistograms(),"Linear WorkspaceIndex property");
}
// Get references to the data in the chosen spectrum
const MantidVec& X = inputWorkspace->dataX(histNumber);
const MantidVec& Y = inputWorkspace->dataY(histNumber);
const MantidVec& E = inputWorkspace->dataE(histNumber);
// Check if this spectrum has errors
double errorsCount = 0.0;
// Retrieve the Start/EndX properties, if set
this->setRange(X,Y);
const bool isHistogram = inputWorkspace->isHistogramData();
// If the spectrum to be fitted has masked bins, we want to exclude them (even if only partially masked)
const MatrixWorkspace::MaskList * const maskedBins =
( inputWorkspace->hasMaskedBins(histNumber) ? &(inputWorkspace->maskedBins(histNumber)) : NULL );
// Put indices of masked bins into a set for easy searching later
std::set<size_t> maskedIndices;
if (maskedBins)
{
MatrixWorkspace::MaskList::const_iterator it;
for (it = maskedBins->begin(); it != maskedBins->end(); ++it)
maskedIndices.insert(it->first);
}
progress(0);
// Declare temporary vectors and reserve enough space if they're going to be used
std::vector<double> XCen, unmaskedY, weights;
int numPoints = m_maxX - m_minX;
if (isHistogram) XCen.reserve(numPoints);
if (maskedBins) unmaskedY.reserve(numPoints);
weights.reserve(numPoints);
for (int i = 0; i < numPoints; ++i)
{
// If the current bin is masked, skip it
if ( maskedBins && maskedIndices.count(m_minX+i) ) continue;
// Need to adjust X to centre of bin, if a histogram
if (isHistogram) XCen.push_back( 0.5*(X[m_minX+i]+X[m_minX+i+1]) );
// If there are masked bins present, we need to copy the unmasked Y values
if (maskedBins) unmaskedY.push_back(Y[m_minX+i]);
// GSL wants the errors as weights, i.e. 1/sigma^2
// We need to be careful if E is zero because that would naively lead to an infinite weight on the point.
// Solution taken here is to zero weight if error is zero, which typically means Y is zero
// (so it is effectively excluded from the fit).
const double& currentE = E[m_minX+i];
weights.push_back( currentE ? 1.0/(currentE*currentE) : 0.0 );
// However, if the spectrum given has all errors of zero, then we should use the gsl function that
// doesn't take account of the errors.
if ( currentE ) ++errorsCount;
}
progress(0.3);
// If masked bins present, need to recalculate numPoints here
if (maskedBins) numPoints = static_cast<int>(unmaskedY.size());
// If no points left for any reason, bail out
if (numPoints == 0)
{
g_log.error("No points in this range to fit");
throw std::runtime_error("No points in this range to fit");
}
// Set up pointer variables to pass to gsl, pointing them to the right place
const double * const xVals = ( isHistogram ? &XCen[0] : &X[m_minX] );
const double * const yVals = ( maskedBins ? &unmaskedY[0] : &Y[m_minX] );
// Call the gsl fitting function
// The stride value of 1 reflects that fact that we want every element of our input vectors
const int stride = 1;
double *c0(new double),*c1(new double),*cov00(new double),*cov01(new double),*cov11(new double),*chisq(new double);
int status;
// Unless our spectrum has error values for vast majority of points,
// call the gsl function that doesn't use errors
if ( errorsCount/numPoints < 0.9 )
{
g_log.debug("Calling gsl_fit_linear (doesn't use errors in fit)");
status = gsl_fit_linear(xVals,stride,yVals,stride,numPoints,c0,c1,cov00,cov01,cov11,chisq);
}
// Otherwise, call the one that does account for errors on the data points
else
{
g_log.debug("Calling gsl_fit_wlinear (uses errors in fit)");
status = gsl_fit_wlinear(xVals,stride,&weights[0],stride,yVals,stride,numPoints,c0,c1,cov00,cov01,cov11,chisq);
}
progress(0.8);
// Check that the fit succeeded
std::string fitStatus = gsl_strerror(status);
// For some reason, a fit where c0,c1 & chisq are all infinity doesn't report as a
// failure, so check explicitly.
if ( !gsl_finite(*chisq) || !gsl_finite(*c0) || !gsl_finite(*c1) )
fitStatus = "Fit gives infinities";
if (fitStatus != "success") g_log.error() << "The fit failed: " << fitStatus << "\n";
else
g_log.information() << "The fit succeeded, giving y = " << *c0 << " + " << *c1 << "*x, with a Chi^2 of " << *chisq << "\n";
// Set the fit result output properties
setProperty("FitStatus",fitStatus);
setProperty("FitIntercept",*c0);
setProperty("FitSlope",*c1);
setProperty("Cov00",*cov00);
setProperty("Cov11",*cov11);
setProperty("Cov01",*cov01);
setProperty("Chi2",*chisq);
// Create and fill a workspace2D with the same bins as the fitted spectrum and the value of the fit for the centre of each bin
const size_t YSize = Y.size();
MatrixWorkspace_sptr outputWorkspace = WorkspaceFactory::Instance().create(inputWorkspace,1,X.size(),YSize);
// Copy over the X bins
outputWorkspace->dataX(0).assign(X.begin(),X.end());
// Now loop over the spectrum and use gsl function to calculate the Y & E values for the function
for (size_t i = 0; i < YSize; ++i)
{
const double x = ( isHistogram ? 0.5*(X[i]+X[i+1]) : X[i] );
const int err = gsl_fit_linear_est(x,*c0,*c1,*cov00,*cov01,*cov11,&(outputWorkspace->dataY(0)[i]),&(outputWorkspace->dataE(0)[i]));
if (err) g_log.warning() << "Problem in filling the output workspace: " << gsl_strerror(err) << std::endl;
}
setProperty("OutputWorkspace",outputWorkspace);
progress(1);
// Clean up
delete c0;
delete c1;
delete cov00;
delete cov01;
delete cov11;
delete chisq;
}
