jhplot.math.num.root

Class BrentRootFinder

java.lang.Object

jhplot.math.num.IterativeMethod

jhplot.math.num.root.BrentRootFinder

public class BrentRootFinder
extends IterativeMethod

Brent's 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 Brent's method root finder is created with the above function:

 BrentRootFinder finder = new BrentRootFinder(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. Wikipedia contributors, "Brent's method," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Brent%27s_method&oldid=132341223

Since:

1.1

Nested Class Summary

Nested classes/interfaces inherited from class jhplot.math.num.IterativeMethod

IterativeMethod.IterativeState

Constructor Summary

Constructors

Constructor and Description
BrentRootFinder(Function f) Create a root finder for the given function.
BrentRootFinder(Function f, int iterations, double error) Create a root finder for the given function.

Method Summary

Modifier and Type	Method and Description
double	findRoot(double min, double max) Find a root of the target function that lies between the two initial approximations, x0 and x1.
Function	getFunction() Access the target function.
void	setFunction(Function f) Modify the target function.

Methods inherited from class jhplot.math.num.IterativeMethod

getMaximumIterations, getMaximumRelativeError, iterate, setMaximumIterations, setMaximumRelativeError

Methods inherited from class java.lang.Object

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

Constructor Detail

BrentRootFinder

public BrentRootFinder(Function f)

Create a root finder for the given function.

Parameters:

f - the target function.

BrentRootFinder

public BrentRootFinder(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 between the two initial approximations, x0 and x1.

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.