statistics.h File Reference

#include <cstdio>
#include <tuple>
#include "gromacs/utility/real.h"

Include dependency graph for statistics.h:

Description

Declares simple statistics toolbox.

Authors

David van der Spoel david.nosp@m..van.nosp@m.dersp.nosp@m.oel@.nosp@m.icm.u.nosp@m.u.se

Typedefs
typedef struct gmx_stats *	gmx_stats_t
	Abstract container type.

Enumerations
enum	{   elsqWEIGHT_NONE, elsqWEIGHT_X, elsqWEIGHT_Y, elsqWEIGHT_XY,   elsqWEIGHT_NR }
	Enum for statistical weights.

Functions
gmx_stats_t	gmx_stats_init ()
	Initiate a data structure. More...
void	gmx_stats_free (gmx_stats_t stats)
	Destroy a data structure. More...
void	gmx_stats_add_point (gmx_stats_t stats, double x, double y, double dx, double dy)
	Add a point to the data set. More...
void	gmx_stats_get_ab (gmx_stats_t stats, int weight, real *a, real *b, real *da, real *db, real *chi2, real *Rfit)
	Fit the data to y = ax + b, possibly weighted, if uncertainties have been input. da and db may be NULL. More...
real	gmx_stats_get_average (gmx_stats_t stats)
	Computes and returns the average value. More...
std::tuple< real, real, real >	gmx_stats_get_ase (gmx_stats_t stats)
	Pointers may be null, in which case no assignment will be done. More...
void	lsq_y_ax_b (int n, real x[], real y[], real *a, real *b, real *r, real *chi2)
	Fit a straight line y=ax+b thru the n data points x, y. More...
void	lsq_y_ax_b_xdouble (int n, double x[], real y[], real *a, real *b, real *r, real *chi2)
	Fit a straight line y=ax+b thru the n data points x, y. More...
void	lsq_y_ax_b_error (int n, real x[], real y[], real dy[], real *a, real *b, real *da, real *db, real *r, real *chi2)
	Fit a straight line y=ax+b thru the n data points x, y. More...

Function Documentation

void gmx_stats_add_point	(	gmx_stats_t	stats,
		double	x,
		double	y,
		double	dx,
		double	dy
	)

Add a point to the data set.

Parameters

[in]	stats	The data structure
[in]	x	The x value
[in]	y	The y value
[in]	dx	The error in the x value
[in]	dy	The error in the y value

void gmx_stats_free

(

gmx_stats_t

stats

)

Destroy a data structure.

Parameters

stats

The data structure

void gmx_stats_get_ab	(	gmx_stats_t	stats,
		int	weight,
		real *	a,
		real *	b,
		real *	da,
		real *	db,
		real *	chi2,
		real *	Rfit
	)

Fit the data to y = ax + b, possibly weighted, if uncertainties have been input. da and db may be NULL.

Parameters

[in]	stats	The data structure
[in]	weight	type of weighting
[out]	a	slope
[out]	b	intercept
[out]	da	sigma in a
[out]	db	sigma in b
[out]	chi2	normalized quality of fit
[out]	Rfit	correlation coefficient

std::tuple<real, real, real> gmx_stats_get_ase

(

gmx_stats_t

stats

)

Pointers may be null, in which case no assignment will be done.

Parameters

[in]

stats

The data structure

Returns

Tuple of (average value, its standard deviation, its standard error)

Exceptions

InconsistentInputError

if given no points to analyze

real gmx_stats_get_average

(

gmx_stats_t

stats

)

Computes and returns the average value.

Parameters

[in]

stats

The data structure

Returns

Average value

Exceptions

InconsistentInputError

if given no points to average

gmx_stats_t gmx_stats_init

(

)

Initiate a data structure.

Returns

the data structure

void lsq_y_ax_b	(	int	n,
		real	x[],
		real	y[],
		real *	a,
		real *	b,
		real *	r,
		real *	chi2
	)

Fit a straight line y=ax+b thru the n data points x, y.

Parameters

[in]	n	number of points
[in]	x	data points x
[in]	y	data point y
[out]	a	slope
[out]	b	intercept
[out]	r	correlation coefficient
[out]	chi2	quality of fit

Exceptions

InconsistentInputError

if given no points to fit

void lsq_y_ax_b_error	(	int	n,
		real	x[],
		real	y[],
		real	dy[],
		real *	a,
		real *	b,
		real *	da,
		real *	db,
		real *	r,
		real *	chi2
	)

Fit a straight line y=ax+b thru the n data points x, y.

Parameters

[in]	n	number of points
[in]	x	data points x
[in]	y	data point y
[in]	dy	uncertainty in data point y
[out]	a	slope
[out]	b	intercept
[out]	da	error in slope
[out]	db	error in intercept
[out]	r	correlation coefficient
[out]	chi2	quality of fit

Exceptions

InconsistentInputError

if given no points to fit

void lsq_y_ax_b_xdouble	(	int	n,
		double	x[],
		real	y[],
		real *	a,
		real *	b,
		real *	r,
		real *	chi2
	)

Fit a straight line y=ax+b thru the n data points x, y.

Parameters

[in]	n	number of points
[in]	x	data points x
[in]	y	data point y
[out]	a	slope
[out]	b	intercept
[out]	r	correlation coefficient
[out]	chi2	quality of fit

Exceptions

InconsistentInputError

if given no points to fit Suits cases where x is already always computed in double precision even in a mixed-precision build configuration.