Mathematics and Statistics

Data Structures
struct	pj_math_stat

Macros
#define	PJ_PI   3.14159265358979323846 /* pi */
#define	PJ_1_PI   0.318309886183790671538 /* 1/pi */
#define	PJ_ABS(x)   ((x) > 0 ? (x) : -(x))
#define	PJ_MAX(x, y)   ((x) > (y)? (x) : (y))
#define	PJ_MIN(x, y)   ((x) < (y)? (x) : (y))

Functions
unsigned	pj_isqrt (unsigned i)
void	pj_math_stat_init (pj_math_stat *stat)
void	pj_math_stat_update (pj_math_stat *stat, int val)
unsigned	pj_math_stat_get_stddev (const pj_math_stat *stat)
void	pj_math_stat_set_stddev (pj_math_stat *stat, unsigned dev)

Detailed Description

Provides common mathematics constants and operations, and also standard statistics calculation (min, max, mean, standard deviation). Statistics calculation is done in realtime (statistics state is updated on time each new sample comes).

Macro Definition Documentation

PJ_1_PI

#define PJ_1_PI   0.318309886183790671538 /* 1/pi */

1/pi

PJ_ABS

#define PJ_ABS

(

x

)

((x) > 0 ? (x) : -(x))

Mathematical macros Get the absolute value

PJ_MAX

#define PJ_MAX	(		x,
			y
	)		((x) > (y)? (x) : (y))

Get the maximum of two values

PJ_MIN

#define PJ_MIN	(		x,
			y
	)		((x) < (y)? (x) : (y))

Get the minimum of two values

PJ_PI

#define PJ_PI   3.14159265358979323846 /* pi */

Mathematical constants pi

Function Documentation

pj_isqrt()

unsigned pj_isqrt

(

unsigned

i

)

Calculate integer square root of an integer.

Parameters

i	Integer to be calculated.

Returns

Square root result.

Referenced by pj_math_stat_get_stddev().

pj_math_stat_get_stddev()

unsigned pj_math_stat_get_stddev

(

const pj_math_stat *

stat

)

Get the standard deviation of specified statistics state.

Parameters

stat	Statistic state.

Returns

The standard deviation.

References pj_math_stat::m2_, pj_math_stat::n, and pj_isqrt().

pj_math_stat_init()

void pj_math_stat_init

(

pj_math_stat *

stat

)

Initialize statistics state.

Parameters

stat	Statistic state.

References pj_bzero().

pj_math_stat_set_stddev()

void pj_math_stat_set_stddev	(	pj_math_stat *	stat,
		unsigned	dev
	)

Set the standard deviation of statistics state. This is useful when the statistic state is operated in 'read-only' mode as a storage of statistical data.

Parameters

stat	Statistic state.
dev	The standard deviation.

References pj_math_stat::m2_, and pj_math_stat::n.

pj_math_stat_update()

void pj_math_stat_update	(	pj_math_stat *	stat,
		int	val
	)

Update statistics state as a new sample comes.

Parameters

stat	Statistic state.
val	The new sample data.

References pj_math_stat::last, pj_math_stat::m2_, pj_math_stat::max, pj_math_stat::mean, pj_math_stat::mean_res_, pj_math_stat::min, and pj_math_stat::n.