USGS Astrogeology Isis API

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.

Definition at line 61 of file 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	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.
Private Attributes
Isis::Statistics	p_x
	A Statistics object holding x data.
Isis::Statistics	p_y
	A Statistics object holding y data.
double	p_sumxy
	The sum of x and y.
BigInt	p_validPixels
	The number of valid (computed) pixels.
BigInt	p_invalidPixels
	The number of invalid (ignored) pixels.
BigInt	p_totalPixels
	The total number of pixels (invalid and valid).

Constructor & Destructor Documentation

Isis::MultivariateStatistics::MultivariateStatistics ( )

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

Definition at line 36 of file MultivariateStatistics.cpp.

References Reset().

Isis::MultivariateStatistics::~MultivariateStatistics ( )

Destructs a MultivariateStatistics object.

Definition at line 52 of file MultivariateStatistics.cpp.

Member Function Documentation

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.

Definition at line 62 of file MultivariateStatistics.cpp.

References Isis::Statistics::AddData(), Isis::IsValidPixel(), p_invalidPixels, p_sumxy, p_totalPixels, p_validPixels, p_x, and p_y.

Referenced by Isis::MaximumCorrelation::MatchAlgorithm().

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.

Definition at line 138 of file MultivariateStatistics.cpp.

References Covariance(), Isis::NULL8, p_validPixels, p_x, p_y, and Isis::Statistics::StandardDeviation().

Referenced by Isis::MaximumCorrelation::MatchAlgorithm().

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.