Isis::MultivariateStatistics Class Reference
[Statistics]

Container of multivariate statistics. More...

#include <MultivariateStatistics.h>

Public Member Functions
	MultivariateStatistics ()
	Constructs a Multivariate Statistics object with accumulators and counters set to zero.
	~MultivariateStatistics ()
	Destructs a MultivariateStatistics object.
void	Reset ()
	Resets all accumulators to zero.
void	AddData (const double x, const double y, const unsigned int count)
	Add two arrays of doubles to the accumulators and counters.
void	AddData (double x, double y, unsigned int count=1)
	Add an x,y value to the accumulators and counters count times.
void	RemoveData (const double x, const double y, const unsigned int count)
	Remove an array of doubles from the accumulators and counters.
Isis::Statistics	X () const
	Returns a Stats object for all of the X data fed through the AddData method.
Isis::Statistics	Y () const
	Returns a Stats object for all of the Y data fed through the AddData method.
double	SumXY () const
	Returns the sum of x*y for all data given through the AddData method.
double	Covariance () const
	Computes and returns the covariance between the two data sets If there are no valid data (pixels) then NULL8 is returned.
double	Correlation () const
	Computes and returns the coefficient of correlation (between -1.0 and 1.0) of the two data sets.
void	LinearRegression (double &a, double &b) const
	Fits a line $y=A+Bx$ through the data.
BigInt	ValidPixels () const
	Returns the number of valid pixels processed.
BigInt	InvalidPixels () const
	Returns the number of invalid pixels encountered.
BigInt	TotalPixels () const
	Returns the total number of pixels processed.

Detailed Description

Container of multivariate statistics.

This class is used to accumulate multivariate statisics on two double arrays. In particular, it is highly useful for obtaining the covariance, correlation, and linear regression analysis on the the data. It ignores input values which are Isis special pixel values. That is, if either co-aligned double value is a special pixel then both values are not used in any statistical computation.

See also:: Histogram; Stats

Author:: 2004-06-08 Jeff Anderson

Constructor & Destructor Documentation

Isis::MultivariateStatistics::MultivariateStatistics ( )

Constructs a Multivariate Statistics object with accumulators and counters set to zero.

Isis::MultivariateStatistics::~MultivariateStatistics ( )

Destructs a MultivariateStatistics object.

Member Function Documentation

void Isis::MultivariateStatistics::AddData	(	double	x,
		double	y,
		unsigned int	count = `1`
	)

Add an x,y value to the accumulators and counters count times.

This method can be invoked multiple times before obtaining statistics.

Parameters:

	x	x value to add
	y	y value to add
	count	Number of times to add this x,y value

void Isis::MultivariateStatistics::AddData	(	const double *	x,
		const double *	y,
		const unsigned int	count
	)

Add two arrays of doubles to the accumulators and counters.

This method can be invoked multiple times, for example, once for each line in a cube, before obtaining statistics.

Parameters:

	x	Array of doubles to add.
	y	Array of doubles to add.
	count	Number of doubles to process.

double Isis::MultivariateStatistics::Correlation ( ) const

Computes and returns the coefficient of correlation (between -1.0 and 1.0) of the two data sets.

This can be used as a goodness-of-fit measurement. The close the correlation is two -1.0 or 1.0 the more likely the data sets are related (and therefore the regression equation is valid).

Returns:: The coefficient of correlation. (between -1.0 and 1.0) The closer to 0.0 implies there is less correlation between the data sets. Returns NULL8 if correlation couldn't be computed.

Referenced by Isis::OverlapStatistics::toPvl().

double Isis::MultivariateStatistics::Covariance ( ) const

Computes and returns the covariance between the two data sets If there are no valid data (pixels) then NULL8 is returned.