vec_math
Class SimpleDifferentiator

java.lang.Object
  vec_math.SimpleDifferentiator

All Implemented Interfaces:

Differentiator

public class SimpleDifferentiator
extends Object
implements Differentiator

The simpliest Differentiator possible. Take the last two y-values and divide their difference by the stepsize.

Nested Class Summary

static class

SimpleDifferentiator.E Tests the integrator.

Field Summary

private double	xlast The x-value at the last call to add.
private double	xprior The x-value prior-to-last.
private double	ylast The y-value at the last call to add.
private double	yprior The y-value prior-to-last.

Constructor Summary

SimpleDifferentiator()
Defaults the xprior to zero and the xlast value to one, mimicing a step-size of one.

Method Summary

void	add(double y) Adds a new y-data point.
void	add(double x, double y) Adds a new x/y data point.
double	getDerivative() Calculates the difference at the last points added.
double	getDerivative(double x) Cannot compute.
void	setData(double[] y) Takes the last two y-values as the last and prior-to-last y value.
void	setData(double[] x, double[] y) Takes the last two values of x and stores them for the step size.

Methods inherited from class java.lang.Object

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

Field Detail

xlast

private double xlast

The x-value at the last call to add.

xprior

private double xprior

The x-value prior-to-last.

ylast

private double ylast

The y-value at the last call to add.

yprior

private double yprior

The y-value prior-to-last.

Constructor Detail

SimpleDifferentiator

public SimpleDifferentiator()

Defaults the xprior to zero and the xlast value to one, mimicing a step-size of one. This step-size is used in equally-spaced differentiator methods, where x is never set.

Method Detail

setData

public void setData(double[] x,
                    double[] y)

Takes the last two values of x and stores them for the step size. Then calls the set-data method with the y-array as an argument. Note that for high-speed, only equal-step size should be used, calling directly the set-data-in-y method.

Specified by:

setData in interface Differentiator

Parameters:

x - A double-array representing the x-axis values.

y - A double-array representing the y-axis values.

setData

public void setData(double[] y)

Takes the last two y-values as the last and prior-to-last y value.

Specified by:

setData in interface Differentiator

Parameters:

y - A double-array representing the y-axis values.

add

public void add(double x,
                double y)

Adds a new x/y data point. Transfers xlast to xprior and stors the x-value passed over in xlast. Then, call the add-method with the y-value alone.

Specified by:

add in interface Differentiator

Parameters:

x - A newly added x-value.

y - A newly added y-value.

add

public void add(double y)

Adds a new y-data point. Transfers ylast to yprior and stors the y-value passed over in ylast.

Specified by:

add in interface Differentiator

Parameters:

y - A newly added y-value.

getDerivative

public double getDerivative()

Calculates the difference at the last points added. If the equal- stepped version is used, the step size is calculated from the default setting done in the construction phase. Note that deliberate missuse (i.e. calling add with x/y, then adding only y values) can yield wrong results.

Specified by:

getDerivative in interface Differentiator

Returns:

The difference of the y-values devided by the stepsize in x.

getDerivative

public double getDerivative(double x)

Cannot compute.

Specified by:

getDerivative in interface Differentiator