casacore::StatAcc< T > Class Template Reference

A statistics accumulator More...

#include <StatAcc.h>

Public Member Functions
	StatAcc ()
	constructors and destructor. More...
	StatAcc (const StatAcc &)
	~StatAcc ()
void	reset ()
	Reset or copy the accumulator attributes. More...
void	copy (const StatAcc &)
StatAcc &	operator= (const StatAcc &)
	Operators for adding and copying accumulators. More...
StatAcc	operator+ (const StatAcc &)
StatAcc &	operator+= (const StatAcc &)
void	put (const T v)
	Accumulate input value(s) v with weight w. More...
void	put (const T v, const Float w)
void	put (const Array< T > &v)
void	put (const Array< T > &v, const Array< Float > &w)
void	put (const Block< T > &v)
void	put (const Block< T > &v, const Block< Float > &w)
Double	getWtot () const
	Get statistics results one at a time. More...
uInt	getCount () const
Fallible< Double >	getMin () const
Fallible< Double >	getMax () const
Fallible< Double >	getMean () const
Fallible< Double >	getRms () const
Fallible< Double >	getVariance () const
Fallible< Double >	getRmsAbs () const
void	printSummaryList (std::ostream &, const String &caption) const
	Print summary of accumulated statistics. More...
void	printSummaryLine (std::ostream &, const String &caption) const
void	printSummaryLineHeader (std::ostream &, const String &caption) const

Private Member Functions
void	put1 (const T, const Float)
	Accumulate a single weighted value. More...

Private Attributes
Double	itsWtot
Double	itsWsum
Double	itsWssum
Double	itsMin
Double	itsMax
uInt	itsCount

Detailed Description

template<class T>
class casacore::StatAcc< T >

A statistics accumulator

Review Status

Test programs:

tStatAcc

Prerequisite

• module Arrays
• Arrays module

Etymology

StatAcc stands for ‘Statistics Accumulator’.

Template Type Argument Requirements (T)

• A statistics accumulator accepts (weighted) input values and calculates simple statistice (min, max, weighted mean, rms etc). The accepted input types are real, i.e. Int, uInt, Float, Double, but not Complex. The reason for this is that the < operator of Complex (needed for min/max) works on the norm in any case, and the sqrt function (needed for rms) yields an ambiguous result.

  Restriction to real types also allows the internal arithmetic type to be Double rather than the input type. The latter would give all kinds of complications with weighting, accuracy and overflow if the input type would be Int or uInt.

Synopsis

The (weighted) values are fed to StatAcc via the member function ‘put’. They can be fed individually, or in the form of an Array. The weights are optional (default = 1) and always have type Float.

Asking for a result does not change the internal state. The type of the returned results is always Fallible<Double>. A result is invalid if no input values with non-zero weight have been accumulated yet.

The accumulator can be re-initialised with the function ‘reset’. Accumulators can be added to each other, which is as if their combined values had been accumulated in the same accumulator.

Some functions have been provided to display a summary of the statistics results. One may choose between a one-line format (with an optional associated header line), and a list.

Example

 StatAcc<T> s;               // T is Float, Double, Int etc
 Matrix<T> vv(2,5);          // a matrix (array) of input values
 Matrix<Float> wgt(2,5);     // an associated matrix of weights
.... fill vv and wgt with values and individual weights..\.
 s.put(vv,wgt);              // accumulate the weighted values   
 Fallible<Double> min = s.getMin();    // return the minimum value
 
 s.reset();                  // re-initialise
 s.put(vv);                  // if wgt omitted, default = 1.0
 if (s.getRms().isValid() {  // check validity of rms
... use it..\.
 }

Motivation

One often needs simple statistics of a series of values, which may occur by themselves or in arrays at various points in a program.
Sincs it is a pain to have to assign accumulation variables, and to write statistics evaluation code (including exceptions), this helper class is provided.

Definition at line 125 of file StatAcc.h.

Constructor & Destructor Documentation

StatAcc() [1/2]

template<class T >

casacore::StatAcc< T >::StatAcc

(

)

constructors and destructor.

StatAcc() [2/2]

template<class T >

casacore::StatAcc< T >::StatAcc

(

const StatAcc< T > &

)

~StatAcc()

template<class T >

casacore::StatAcc< T >::~StatAcc ( )

inline

Definition at line 131 of file StatAcc.h.

Member Function Documentation

copy()

template<class T >

void casacore::StatAcc< T >::copy

(

const StatAcc< T > &

)

getCount()

template<class T >

uInt casacore::StatAcc< T >::getCount

(

)

const

getMax()

template<class T >

Fallible<Double> casacore::StatAcc< T >::getMax

(

)

const

getMean()

template<class T >

Fallible<Double> casacore::StatAcc< T >::getMean

(

)

const

getMin()

template<class T >

Fallible<Double> casacore::StatAcc< T >::getMin

(

)

const

getRms()

template<class T >

Fallible<Double> casacore::StatAcc< T >::getRms

(

)

const

getRmsAbs()

template<class T >

Fallible<Double> casacore::StatAcc< T >::getRmsAbs

(

)

const

getVariance()

template<class T >

Fallible<Double> casacore::StatAcc< T >::getVariance

(

)

const

getWtot()

template<class T >

Double casacore::StatAcc< T >::getWtot

(

)

const

Get statistics results one at a time.

Count is the nr of values accumulated. Wtot is the sum of the weights. Rms is defined w.r.t. the mean, and is the square of Variance. RmsAbs is the root-mean-square of the absolute input values.

operator+()

template<class T >

StatAcc casacore::StatAcc< T >::operator+

(

const StatAcc< T > &

)

operator+=()

template<class T >

StatAcc& casacore::StatAcc< T >::operator+=

(

const StatAcc< T > &

)

operator=()

template<class T >

StatAcc& casacore::StatAcc< T >::operator=

(

const StatAcc< T > &

)

Operators for adding and copying accumulators.

printSummaryLine()

template<class T >

void casacore::StatAcc< T >::printSummaryLine	(	std::ostream &	,
		const String &	caption
	)		const

printSummaryLineHeader()

template<class T >

void casacore::StatAcc< T >::printSummaryLineHeader	(	std::ostream &	,
		const String &	caption
	)		const

printSummaryList()

template<class T >

void casacore::StatAcc< T >::printSummaryList	(	std::ostream &	,
		const String &	caption
	)		const

Print summary of accumulated statistics.

Line is a one-line summary, including the (short) caption. LineHeader gives a one-line explanation of the numbers. List uses a separate line for each result (mean, max etc).

put() [1/6]

template<class T >

void casacore::StatAcc< T >::put

(

const Array< T > &

v

)

put() [2/6]

template<class T >

void casacore::StatAcc< T >::put	(	const Array< T > &	v,
		const Array< Float > &	w
	)

put() [3/6]

template<class T >

void casacore::StatAcc< T >::put

(

const Block< T > &

v

)

put() [4/6]

template<class T >

void casacore::StatAcc< T >::put	(	const Block< T > &	v,
		const Block< Float > &	w
	)

put() [5/6]

template<class T >

void casacore::StatAcc< T >::put ( const T  v )

inline

Accumulate input value(s) v with weight w.

If weight is omitted, the default=1.

Definition at line 205 of file StatAcc.h.

put() [6/6]

template<class T >

void casacore::StatAcc< T >::put ( const T  v, const Float  w  )

inline

Definition at line 210 of file StatAcc.h.

put1()

template<class T >

void casacore::StatAcc< T >::put1 ( const  T, const  Float  )

private

Accumulate a single weighted value.

reset()

template<class T >

void casacore::StatAcc< T >::reset

(

)

Reset or copy the accumulator attributes.

Member Data Documentation

itsCount

template<class T >

uInt casacore::StatAcc< T >::itsCount

private

Definition at line 190 of file StatAcc.h.

itsMax

template<class T >

Double casacore::StatAcc< T >::itsMax

private

Definition at line 189 of file StatAcc.h.

itsMin

template<class T >

Double casacore::StatAcc< T >::itsMin

private

Definition at line 188 of file StatAcc.h.

itsWssum

template<class T >

Double casacore::StatAcc< T >::itsWssum

private

Definition at line 187 of file StatAcc.h.

itsWsum

template<class T >

Double casacore::StatAcc< T >::itsWsum

private

Definition at line 186 of file StatAcc.h.

itsWtot

template<class T >

Double casacore::StatAcc< T >::itsWtot

private

Definition at line 185 of file StatAcc.h.

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The documentation for this class was generated from the following file:

• scimath/Mathematics/StatAcc.h