StackMetric.c File Reference

Author:: Creighton, T.Computes the parameter space metric for a coherent pulsar search.

#include <math.h>
#include <lal/LALStdlib.h>
#include <lal/AVFactories.h>
#include <lal/StackMetric.h>

Include dependency graph for StackMetric.c:

Go to the source code of this file.

Functions

NRCSID (STACKMETRICC,"$Id: StackMetric.c,v 1.5 2007/06/08 14:41:51 bema Exp $")

void LALStackMetric (LALStatus *stat, REAL8Vector *metric, REAL8Vector *lambda, MetricParamStruc *params)

Detailed Description

Author:: Creighton, T.Computes the parameter space metric for a coherent pulsar search.

Date:: 2000, 2001

Id: StackMetric.c,v 1.5 2007/06/08 14:41:51 bema Exp

Description

This function computes the metric $g_{\alpha\beta}(\mathbf{\lambda})$ , as discussed in the header StackMetric.h, under the assumption that the detected power is constructed from the incoherent sum of $N$

separate power spectrum, each derived from separate time intervals of length $\Delta t$ . The indecies $\alpha$ and $\beta$ are assumed to run from 0 to $n$

, where

is the total number of ``shape'' parameters.

This routine has exactly the same calling structure and data storage as the LALCoherentMetric() function. Thus, the argument *metric is a vector of length $(n+1)(n+2)/2$ storing all non-redundant coefficients of $g_{\alpha\beta}$ , or twice this length if params->errors is nonzero. See CoherentMetric.c for the indexing scheme. The argument lambda is another vector, of length $n+1$ , storing the components of $\mathbf{\lambda}=(\lambda^0,\ldots,\lambda^n)$ for the parameter space point at which the metric is being evaluated. The argument *params stores the remaining parameters for computing the metric, as given in the Structures section of StackMetric.h.

Algorithm

Most of what this routine does is set up arguments to be passed to the function LALCoherentMetric(). Each metric component in the stack metric is given simply by:

$g_{\alpha\beta}(\mathbf{\lambda}) = \frac{1}{N} \sum_{k=1}^N g^{(k)}_{\alpha\beta}(\mathbf{\lambda}) \; ,$

where $g^{(k)}_{\alpha\beta}$ is just the coherent metric computed on the time interval $[t_\mathrm{start}+(k-1)\Delta t, t_\mathrm{start}+k\Delta t]$ . The estimated uncertainty $s_{\alpha\beta}$ in this component is taken to be:

$s_{\alpha\beta} = \frac{1}{\sqrt{N}} \max_{k\in\{1,\ldots,N\}} s^{(k)}_{\alpha\beta} \; .$

There are no clever tricks involved in any of these computations.

Definition in file StackMetric.c.

Function Documentation

NRCSID	(	STACKMETRICC	,
		"$Id: StackMetric.	c,
		v 1.5 2007/06/08 14:41:51 bema Exp $"
	)

void LALStackMetric	(	LALStatus *	stat,
		REAL8Vector *	metric,
		REAL8Vector *	lambda,
		MetricParamStruc *	params
	)

Definition at line 80 of file StackMetric.c.

Generated on Mon Oct 13 02:33:09 2008 for LAL by

1.5.2


Functions
	NRCSID (STACKMETRICC,"$Id: StackMetric.c,v 1.5 2007/06/08 14:41:51 bema Exp $")
void	LALStackMetric (LALStatus stat, REAL8Vector metric, REAL8Vector lambda, MetricParamStruc params)