Trigger Interpolation

Detailed Description

This module implements several algorithms for performing sub-sample interpolation of peaks in the output of a matched filter.

The interface for each algorithm is the same. To illustrate, here is a description of the interface for the 'Lanczos' algorithm.

There is an opaque data type called LanczosTriggerInterpolant that holds workspaces for performing the interpolation. To create one, call the function XLALCreateLanczosTriggerInterpolant as follows:

LanczosTriggerInterpolant *interp = XLALCreateLanczosTriggerInterpolant(5);

The '5' is the interpolation window. In this example, the interpolation will take into account a given sample, the 5 samples before, and the 5 samples after, for a total of 11 samples.

To apply the interpolant to a time series, call XLALApplyLanczosTriggerInterpolant. It is requried that |y[0]| >= |y[i]| for all i from -window to +window. Suppose that you have a complex array y:

COMPLEX16 y[] = {...};

and suppose that the maximum of |y[i]| occurs at i = 8. To interpolate the time and complex value at which the maximum occurs, do the following:

double tmax;
COMPLEX16 ymax;
int result = XLALApplyLanczosTriggerInterpolant(interp, &tmax, &ymax, &y[8]);

Upon success, the return value of XLALApplyLanczosTriggerInterpolant is zero, the interpolated index of the maximum sample is 8 + *tmax, and the interpolated value is in ymax. Upon failure, the return value is nonzero and neither *tmax nor *ymax are modified.

When you are done, release all of the workspace resources associated with the interpolant with:

XLALDestroyLanczosTriggerInterpolant(interp);

Modules
	Cubic Spline Trigger Interpolant
	Catmull-Rom cubic spline interpolation.
	Lanczos Trigger Interpolant
	Lanczos interpolation.
	Nearest Neighbor Trigger Interpolant
	Nearest-neighbor interpolation.
	Quadratic Fit Trigger Interpolant
	Quadratic fit.