net.sf.doodleproject.numerics4j.root
Class FalsePositionRootFinder

java.lang.Object
  net.sf.doodleproject.numerics4j.IterativeMethod
      net.sf.doodleproject.numerics4j.root.FalsePositionRootFinder

public class FalsePositionRootFinder
extends IterativeMethod

The false position method (1) for finding roots of functions.

For example, to find roots for sine, first a Function is defined:

 Function sine = new Function() {
    public double evaluate(double x) {
        return Math.sin(x);
    }}
 };
 

Then, a false position root finder is created with the above function:

 FalsePositionRootFinder finder = new FalsePositionRootFinder(sine);
 

Lastly, locating roots is accomplished using the findRoot(double, double) method:

 // find the root between 3 and 4.
 double pi = finder.findRoot(3.0, 4.0);
 
 // find the root between -1 and 1.
 double zero = finder.findRoot(-1.0, 1.0);
 

References:

1. Eric W. Weisstein. "Method of False Position." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/MethodofFalsePosition.html

Since:

1.1

Version:

$Revision: 1.2 $ $Date: 2007/10/25 04:44:14 $

Nested Class Summary

Nested classes/interfaces inherited from class net.sf.doodleproject.numerics4j.IterativeMethod

IterativeMethod.IterativeState

Constructor Summary

FalsePositionRootFinder(Function f)
Create a root finder for the given function.

FalsePositionRootFinder(Function f, int iterations, double error)
Create a root finder for the given function.

Method Summary

double	findRoot(double min, double max) Find a root of the target function that lies in the interval [ min, max].
Function	getFunction() Access the target function.
void	setFunction(Function f) Modify the target function.

Methods inherited from class net.sf.doodleproject.numerics4j.IterativeMethod

getMaximumIterations, getMaximumRelativeError, iterate, setMaximumIterations, setMaximumRelativeError

Methods inherited from class java.lang.Object

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

Constructor Detail

FalsePositionRootFinder

public FalsePositionRootFinder(Function f)

Create a root finder for the given function.

Parameters:

f - the target function.

FalsePositionRootFinder

public FalsePositionRootFinder(Function f,
                               int iterations,
                               double error)

Create a root finder for the given function.

Parameters:

f - the target function.

iterations - maximum number of iterations.

error - maximum relative error.

Method Detail

findRoot

public double findRoot(double min,
                       double max)
                throws NumericException

Find a root of the target function that lies in the interval [ min, max].

Parameters:

min - the lower bound of the search interval.

max - the upper bound of the search interval.

Returns:

a root that lies between min and max, inclusive.

Throws:

NumericException - if a root could not be found.

getFunction

public Function getFunction()

Access the target function.

Returns:

the target function.

setFunction

public void setFunction(Function f)

Modify the target function.

Parameters:

f - the new target function.