xal.extension.fit

Class LinearFit

java.lang.Object

xal.extension.fit.LinearFit

public class LinearFit
extends java.lang.Object

Fit a set of x,y data pairs to a line where y = slope * x + intercept.

Field Summary

Fields

Modifier and Type	Field and Description
protected double	_correlationCoefficient
protected double	_intercept
protected boolean	_needsUpdate
protected double	_slope
protected MutableUnivariateStatistics	_xStats
protected MutableUnivariateStatistics	_xxStats
protected MutableUnivariateStatistics	_xyStats
protected MutableUnivariateStatistics	_yStats
protected MutableUnivariateStatistics	_yyStats

Constructor Summary

Constructors

Constructor and Description
LinearFit() Constructor

Method Summary

Modifier and Type	Method and Description
void	addSample(double x, double y) Add a new x,y pair.
double	estimateY(double x) Estimate the dependent variable (y) given the independent variable (x).
double	getCorrelationCoefficient() Get the correlation coefficient.
double	getIntercept() Get the intercept performing a fit if needed.
double	getMeanSquareOrdinateError() Get the mean square error of the y value with respect to the fitted line.
double	getSlope() Get the slope performing a fit if needed.
protected void	performFit() Calculate the slope and intercept.
protected void	performFitIfNeeded() Perform a linear fit if the the fit needs to be updated due to newly added data.
java.lang.String	toString() Generate a string representation of the linear equation.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

_xStats

protected final MutableUnivariateStatistics _xStats

_yStats

protected final MutableUnivariateStatistics _yStats

_xxStats

protected final MutableUnivariateStatistics _xxStats

_xyStats

protected final MutableUnivariateStatistics _xyStats

_yyStats

protected final MutableUnivariateStatistics _yyStats

_needsUpdate

protected boolean _needsUpdate

_slope

protected double _slope

_intercept

protected double _intercept

_correlationCoefficient

protected double _correlationCoefficient

Constructor Detail

LinearFit

public LinearFit()

Constructor

Method Detail

addSample

public void addSample(double x,
                      double y)

Add a new x,y pair.

getSlope

public double getSlope()

Get the slope performing a fit if needed.

Returns:

the fitted slope

getIntercept

public double getIntercept()

Get the intercept performing a fit if needed.

Returns:

the fitted intercept

getCorrelationCoefficient

public double getCorrelationCoefficient()

Get the correlation coefficient.

Returns:

the correlation coefficient.

estimateY

public double estimateY(double x)

Estimate the dependent variable (y) given the independent variable (x).

Parameters:

x - the independent variable

Returns:

the dependent variable

getMeanSquareOrdinateError

public double getMeanSquareOrdinateError()

Get the mean square error of the y value with respect to the fitted line. The square root of this number gives an indication of the uncertainty in y value estimates under certain assumptions about the error distribution.

Returns:

the mean square error of the y value with respect to the fitted line

performFitIfNeeded

protected void performFitIfNeeded()

Perform a linear fit if the the fit needs to be updated due to newly added data.

performFit

protected void performFit()

Calculate the slope and intercept.

toString

public java.lang.String toString()

Generate a string representation of the linear equation.

Overrides:

toString in class java.lang.Object

Returns:

a string representation of the linear equation