hmpdf_covariance.h File Reference

#include "hmpdf_object.h"

Functions
int	hmpdf_get_cov (hmpdf_obj *d, int Nbins, double binedges[Nbins+1], double cov[Nbins *Nbins], int noisy)
int	hmpdf_get_cov_diagnostics (hmpdf_obj *d, int *Nphi, double **phi, double **phiweights, double **corr_diagn)

Function Documentation

hmpdf_get_cov()

int hmpdf_get_cov	(	hmpdf_obj *	d,
		int	Nbins,
		double	binedges[Nbins+1],
		double	cov[Nbins *Nbins],
		int	noisy
	)

Returns the covariance matrix of the one-point PDF.

Parameters

[in,out]	d	hmpdf_init() must have been called on d
[in]	Nbins	number of bins the covariance matrix will be binned into
[in]	binedges	monotonically increasing array of length Nbins+1
[out]	cov	the binned covariance matrix will be written into the first Nbins*Nbins elements of this output array
[in]	noisy	if set to non-zero, the covariance matrix will include Gaussian noise with power spectrum hmpdf_noise_pwr.

Returns

error code

Remarks

If the covariance matrix has already been computed and since then no hmpdf_init() has been called on d, the pre-computed result is used and only the binning is performed.

If hmpdf_verbosity is set to a positive value, status updates with estimated remaining time will be given during execution.

The covariance matrix is normalized for a hypothetical all-sky survey. You will have to divide by your sky coverage fsky to get the correct one on your specific application.

hmpdf_get_cov_diagnostics()

int hmpdf_get_cov_diagnostics	(	hmpdf_obj *	d,
		int *	Nphi,
		double **	phi,
		double **	phiweights,
		double **	corr_diagn
	)

Returns diagnostic outputs for the covariance matrix computation. The main use of this function is to identify numerical instability at small pixel separations.

Parameters

[in,out]	d	hmpdf_init() must have been called on d
[out]	Nphi	the number of pixel separations will be written into the return value
[out]	phi	pointer will be set to an array of length Nphi, containing the pixel separations used internally (in radians)
[out]	phiweights	pointer will be set to an array of length Nphi, containing the weights assigned to each pixel separation in the summation. This can occasionally be used to tune the hmpdf_pixelexact_max option.
[out]	corr_diagn	pointer will be set to an array of length Nphi, containing the correlation function at the pixel separation sample points. Noisy behaviour at small phi is a sign of numerical instability.

Returns

error code

Remarks

the values in the phi-array are not ordered

you can pass NULL for any of the arguments (apart from the first of course), if you are not interested in that specific output

if the covariance matrix has not already been computed [hmpdf_get_cov() has not been called before], this function will do it

while the code does perform the memory allocation for phi, phiweights, and corr_diagn (so that the user does not have to figure out Nphi beforehand), the user is responsible for freeing these arrays, i.e. to call

free(*phi); free(*phiweights); free(*corr_diagn);

after use.