/** Executes the algorithm * */ void SplineBackground::exec() { API::MatrixWorkspace_sptr inWS = getProperty("InputWorkspace"); int spec = getProperty("WorkspaceIndex"); if (spec > static_cast<int>(inWS->getNumberHistograms())) throw std::out_of_range("WorkspaceIndex is out of range."); const MantidVec& X = inWS->readX(spec); const MantidVec& Y = inWS->readY(spec); const MantidVec& E = inWS->readE(spec); const bool isHistogram = inWS->isHistogramData(); const int ncoeffs = getProperty("NCoeff"); const int k = 4; // order of the spline + 1 (cubic) const int nbreak = ncoeffs - (k - 2); if (nbreak <= 0) throw std::out_of_range("Too low NCoeff"); gsl_bspline_workspace *bw; gsl_vector *B; gsl_vector *c, *w, *x, *y; gsl_matrix *Z, *cov; gsl_multifit_linear_workspace *mw; double chisq; int n = static_cast<int>(Y.size()); bool isMasked = inWS->hasMaskedBins(spec); std::vector<int> masked(Y.size()); if (isMasked) { for(API::MatrixWorkspace::MaskList::const_iterator it=inWS->maskedBins(spec).begin();it!=inWS->maskedBins(spec).end();++it) masked[it->first] = 1; n -= static_cast<int>(inWS->maskedBins(spec).size()); } if (n < ncoeffs) { g_log.error("Too many basis functions (NCoeff)"); throw std::out_of_range("Too many basis functions (NCoeff)"); } /* allocate a cubic bspline workspace (k = 4) */ bw = gsl_bspline_alloc(k, nbreak); B = gsl_vector_alloc(ncoeffs); x = gsl_vector_alloc(n); y = gsl_vector_alloc(n); Z = gsl_matrix_alloc(n, ncoeffs); c = gsl_vector_alloc(ncoeffs); w = gsl_vector_alloc(n); cov = gsl_matrix_alloc(ncoeffs, ncoeffs); mw = gsl_multifit_linear_alloc(n, ncoeffs); /* this is the data to be fitted */ int j = 0; for (MantidVec::size_type i = 0; i < Y.size(); ++i) { if (isMasked && masked[i]) continue; gsl_vector_set(x, j, (isHistogram ? (0.5*(X[i]+X[i+1])) : X[i])); // Middle of the bins, if a histogram gsl_vector_set(y, j, Y[i]); gsl_vector_set(w, j, E[i]>0.?1./(E[i]*E[i]):0.); ++j; } if (n != j) { gsl_bspline_free(bw); gsl_vector_free(B); gsl_vector_free(x); gsl_vector_free(y); gsl_matrix_free(Z); gsl_vector_free(c); gsl_vector_free(w); gsl_matrix_free(cov); gsl_multifit_linear_free(mw); throw std::runtime_error("Assertion failed: n != j"); } double xStart = X.front(); double xEnd = X.back(); /* use uniform breakpoints */ gsl_bspline_knots_uniform(xStart, xEnd, bw); /* construct the fit matrix X */ for (int i = 0; i < n; ++i) { double xi=gsl_vector_get(x, i); /* compute B_j(xi) for all j */ gsl_bspline_eval(xi, B, bw); /* fill in row i of X */ for (j = 0; j < ncoeffs; ++j) { double Bj = gsl_vector_get(B, j); gsl_matrix_set(Z, i, j, Bj); } } /* do the fit */ gsl_multifit_wlinear(Z, w, y, c, cov, &chisq, mw); /* output the smoothed curve */ API::MatrixWorkspace_sptr outWS = WorkspaceFactory::Instance().create(inWS,1,X.size(),Y.size()); { outWS->getAxis(1)->setValue(0, inWS->getAxis(1)->spectraNo(spec)); double xi, yi, yerr; for (MantidVec::size_type i=0;i<Y.size();i++) { xi = X[i]; gsl_bspline_eval(xi, B, bw); gsl_multifit_linear_est(B, c, cov, &yi, &yerr); outWS->dataY(0)[i] = yi; outWS->dataE(0)[i] = yerr; } outWS->dataX(0) = X; } gsl_bspline_free(bw); gsl_vector_free(B); gsl_vector_free(x); gsl_vector_free(y); gsl_matrix_free(Z); gsl_vector_free(c); gsl_vector_free(w); gsl_matrix_free(cov); gsl_multifit_linear_free(mw); setProperty("OutputWorkspace",outWS); }