XploRe Help : nmridders

Keywords - Function groups - @ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Library:	nummath
See also:	nmbrackout nmbrackin nmbrentroot nmbisect nmregfalsi nmsecant

Quantlet:		nmridders
Description:		Ridders' method (regula falsi modification) for finding a root of a given function in a given interval

Reference(s):

Press, W.H., Teukolsky, S.A., Vetterling, W.T., Flannery, B.P. (1992): Numerical Recipes in C, 2nd Edition

Usage:	`root = nmridders(fname {,a0,b0,xtol,maxiter})`
Input:
	`fname`	string, name of a function whose root should be found. The function should have just one scalar parameter x. As a result, the function should return a scalar.
	`a0,b0`	optional scalars, distinct initial points bracketing a root; if not given, nmbrackout will be used to find a bracket
	`xtol`	optional scalar; tolerance - absolute precision of the minimum; default xtol = 1e-8
	`maxiter`	optional scalar; maximal number of iterations; default maxiter = 100
Output:
	`root`	scalar, root of fname (isolated with an approximate precision xtol)

Note:

A warning will be produced if no root is found with a given precision in maxiter iterations.

Example:

library("nummath") proc(fval) = ftion(x) fval = x^2 - 16 endp nmridders("ftion")

Result:

Contents of root
[1,]        4

Example:

library("nummath") proc(fval) = ftion(x) fval = x^2 - 16 endp nmridders("ftion",-10,0)

Result:

Contents of root
[1,]       -4

Author: L. Cizkova, 20030402 license MD*Tech