/**
* Calculates the gradient of chi-square using the experimental data, calculated
* data and errors
* @return : The gradient of chi-square as a vector
*/
std::vector<double> MaxentCalculator::calculateChiGrad() const {
// Calculates the gradient of Chi
// CGrad_i = -2 * [ data_i - dataCalc_i ] / [ error_i ]^2
if ((m_data.size() != m_errors.size()) ||
(m_dataCalc.size() % m_data.size())) {
// Data and errors must have the same number of data points
// but the reconstructed (calculated) data may contain more points
throw std::runtime_error("Cannot compute gradient of Chi");
}
// We only consider the experimental data points to calculate chi grad
size_t sizeDat = m_data.size();
// The number of calculated data points can be bigger than the number of
// experimental data points I am not sure how we should deal with this
// situation. On the one hand one can only consider real data and errors to
// calculate chi-square, but on the other hand this method should return a
// vector of size equal to the size of the calculated data, so I am just
// setting the 'leftovers' to zero. This is what is done in the original
// muon code.
size_t sizeDatCalc = m_dataCalc.size();
std::vector<double> cgrad(sizeDatCalc, 0.);
auto dpoints = static_cast<double>(sizeDat);
for (size_t i = 0; i < sizeDat; i++) {
if (m_errors[i] != 0)
cgrad[i] = -2. * (m_data[i] - m_dataCalc[i]) / m_errors[i] / m_errors[i] /
dpoints;
}
return cgrad;
}
void MainWindow::paintEvent(QPaintEvent *e)
{
QPainter painter(this);
QLinearGradient lgrad(25,100,150,175);
QRadialGradient rgrad(QPoint(100,100),100);
QConicalGradient cgrad(QPoint(100,100),100);
lgrad.setColorAt(0.0,Qt::red);
lgrad.setColorAt(0.5,Qt::green);
lgrad.setColorAt(1.0,Qt::blue);
QRect rect(10,10,200,200);
painter.fillRect(rect,lgrad);
painter.fillRect(rect,rgrad);
painter.fillRect(rect,cgrad);
}
void F77_SUB(cgrad)(int *n, double x[], double grval[]) {
cgrad(n, x, grval) ;
}
