xsh_ksigma_clip.c File Reference

#include <complex.h>
#include <math.h>
#include <string.h>
#include <assert.h>
#include <float.h>
#include <cpl.h>
#include "xsh_ksigma_clip.h"
#include "xsh_detmon_body.h"

Go to the source code of this file.

Macros
#define	CONCAT(a, b)   a ## _ ## b
#define	CONCAT2X(a, b)   CONCAT(a,b)
#define	CPL_TYPE   double
#define	CPL_TYPE   float
#define	CPL_TYPE   int

Functions
static cpl_error_code	xsh_ksigma_clip_double (const double *pi, cpl_binary *pm, int llx, int lly, int urx, int ury, int nx, double var_sum, int npixs, double kappa, int nclip, double tolerance, double *mean, double *stdev)
static cpl_error_code	xsh_ksigma_clip_float (const float *pi, cpl_binary *pm, int llx, int lly, int urx, int ury, int nx, double var_sum, int npixs, double kappa, int nclip, double tolerance, double *mean, double *stdev)
static cpl_error_code	xsh_ksigma_clip_int (const int *pi, cpl_binary *pm, int llx, int lly, int urx, int ury, int nx, double var_sum, int npixs, double kappa, int nclip, double tolerance, double *mean, double *stdev)
cpl_error_code	xsh_ksigma_clip (const cpl_image *img, int llx, int lly, int urx, int ury, double kappa, int nclip, double tolerance, double *kmean, double *kstdev)
	Apply kappa-sigma clipping on input image.

Macro Definition Documentation

CONCAT

#define CONCAT	(		a,
			b
	)		a ## _ ## b

Definition at line 230 of file xsh_ksigma_clip.c.

CONCAT2X

#define CONCAT2X	(		a,
			b
	)		CONCAT(a,b)

Definition at line 231 of file xsh_ksigma_clip.c.

CPL_TYPE [1/3]

#define CPL_TYPE   double

Definition at line 241 of file xsh_ksigma_clip.c.

CPL_TYPE [2/3]

#define CPL_TYPE   float

Definition at line 241 of file xsh_ksigma_clip.c.

CPL_TYPE [3/3]

#define CPL_TYPE   int

Definition at line 241 of file xsh_ksigma_clip.c.

Function Documentation

xsh_ksigma_clip()

cpl_error_code xsh_ksigma_clip	(	const cpl_image *	img,
		int	llx,
		int	lly,
		int	urx,
		int	ury,
		double	kappa,
		int	nclip,
		double	tolerance,
		double *	kmean,
		double *	kstdev
	)

Apply kappa-sigma clipping on input image.

Parameters

img	Input image
llx	Lower left x position (FITS convention)
lly	Lower left y position (FITS convention)
urx	Upper right x position (FITS convention)
ury	Upper right y position (FITS convention)
kappa	Kappa value for the clipping
nclip	Number of clipping iterations
kmean	Mean after clipping (output)
kstdev	Stdev after clipping (output)

Returns

CPL_ERROR_NONE or the relevant #_cpl_error_code_ on error

This function applies an iterative kappa-sigma clipping on the image and returns mean and stdev after the clipping.

The function takes as a starting point the "standard" values of mean and stdev from cpl_stats.

On each iteration, the contribution of pixels outside the range [mean - kappa * stdev, mean + kappa * stdev] is removed, the values of mean and stdev are updated, and so are the limits of the range to be used in the next iteration as well.

The algorithm stops after nclip iterations or when the variation of the range between two consecutive iterations is smaller (absolute value) than the tolerance.

The effectiveness of this function resides on the way the update of the values of mean and stdev is done.

The contribution of a single pixel in variance can be removed as follows:

\sum_{i=1}^{N-1} (x_i - \overline{x}_{n-1})^2 = \sum_{i=1}^ N (x_i - \overline{x}_n )^2 - \frac{N}{N-1} \,( \, \overline{x}_n - x_{n} )^2

For further details on the mathematical aspects, please refer to DFS05126.

Possible #_cpl_error_code_ set in this function:

• CPL_ERROR_NULL_INPUT if img or kmean is NULL
• CPL_ERROR_ILLEGAL_INPUT if a) the window specification is illegal (llx > urx or lly > ury) b) the window specification is outside the image c) the tolerance is negative d) kappa is <= 1.0 e) nclip is <= 0.

The values of kmean and kstdev is undefined on error.

Definition at line 150 of file xsh_ksigma_clip.c.

References kappa, llx, lly, nx, ny, tolerance, urx, and ury.

xsh_ksigma_clip_double()

static cpl_error_code xsh_ksigma_clip_double ( const double *  pi, cpl_binary *  pm, int  llx, int  lly, int  urx, int  ury, int  nx, double  var_sum, int  npixs, double  kappa, int  nclip, double  tolerance, double *  mean, double *  stdev  )

static

xsh_ksigma_clip_float()

static cpl_error_code xsh_ksigma_clip_float ( const float *  pi, cpl_binary *  pm, int  llx, int  lly, int  urx, int  ury, int  nx, double  var_sum, int  npixs, double  kappa, int  nclip, double  tolerance, double *  mean, double *  stdev  )

static

xsh_ksigma_clip_int()

static cpl_error_code xsh_ksigma_clip_int ( const int *  pi, cpl_binary *  pm, int  llx, int  lly, int  urx, int  ury, int  nx, double  var_sum, int  npixs, double  kappa, int  nclip, double  tolerance, double *  mean, double *  stdev  )

static