/**Evaluate a point on the spline. Includes basic error handling
*
* @param x :: Point to evaluate
* @return :: the value of the spline at the given point
*/
double CubicSpline::splineEval(const double x) const {
// calculate the y value
double y = gsl_spline_eval(m_spline.get(), x, m_acc.get());
int errorCode = gsl_spline_eval_e(m_spline.get(), x, m_acc.get(), &y);
// check if GSL function returned an error
checkGSLError(errorCode, GSL_EDOM);
return y;
}
/** Calculate the derivatives of each of the supplied points
*
* @param out :: The array to store the calculated derivatives
* @param xValues :: The array of x values we wish to calculate derivatives at
* @param nData :: The size of the arrays
* @param order :: The order of derivatives to calculate too
*/
void CubicSpline::calculateDerivative(double* out, const double* xValues,
const size_t nData, const size_t order) const
{
double xDeriv = 0;
int errorCode = 0;
bool outOfRange(false);
//throw error if the order is not the 1st or 2nd derivative
if(order < 1) throw std::invalid_argument(
"CubicSpline: order of derivative must be 1 or greater");
for(size_t i = 0; i < nData; ++i)
{
if(checkXInRange(xValues[i]))
{
//choose the order of the derivative
if(order == 1)
{
xDeriv = gsl_spline_eval_deriv(m_spline.get(),xValues[i],m_acc.get());
errorCode = gsl_spline_eval_deriv_e (m_spline.get(),xValues[i],m_acc.get(),&xDeriv);
}
else if (order == 2)
{
xDeriv = gsl_spline_eval_deriv2(m_spline.get(),xValues[i],m_acc.get());
errorCode = gsl_spline_eval_deriv2_e (m_spline.get(),xValues[i],m_acc.get(),&xDeriv);
}
}
else
{
//if out of range, just set it to zero
outOfRange = true;
xDeriv = 0;
}
//check GSL functions didn't return an error
checkGSLError(errorCode, GSL_EDOM);
//record the value
out[i] = xDeriv;
}
//warn user that some values weren't calculated
if(outOfRange)
{
g_log.warning() << "Some x values where out of range and will not be calculated." << std::endl;
}
}
/** Initilize the GSL spline with the given points
*
* @param x :: The x points defining the spline
* @param y :: The y points defining the spline
* @param n :: The size of the arrays
*/
void CubicSpline::initGSLObjects(boost::scoped_array<double>& x, boost::scoped_array<double>& y, int n) const
{
int status = gsl_spline_init(m_spline.get(), x.get(), y.get(), n);
checkGSLError(status, GSL_EINVAL);
}
