/** 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;
}
}
/* Performs the second derivative of a spline */
double FC_FUNC_(oct_spline_eval_der2, OCT_SPLINE_EVAL_DER2)
(const double *x, const void **spl, void **acc)
{
/* the GSL headers specify double x */
return gsl_spline_eval_deriv2((gsl_spline *)(*spl), *x, (gsl_interp_accel *)(*acc));
}
double Interpolate::deriv2(double x) {
return gsl_spline_eval_deriv2 (_spline, x, _acc);
}
