29 July 2010

Root Finding or finding Inverse function

Written by Amit Panchal, Posted in Blog

Hello Friends,
In this post i will explain you how to get the inverse of a function or how to find the root of a function.
suppose there is a function y=f(x)
and you want the value of x when the y is 0 or something else.
you can find this solution using Numerical analytical mathamatics.
to use this algorithms.
download the source code from CodeProject
in this you will find a RootFinding.dll in source folder.
add reference of that file in your project.
and now you just need to make a class to use this dll.

using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using RootFinding;
/// Summary description for RootFinder
public class RootFinder
    public RootFinder()
        // TODO: Add constructor logic here
    // Newtons formel for iterativ lignings løsning
   private static double f (double x) {
        return (x*x-2*x+1); //replace this function by urs
   public static double FindRoot(double x,double s,double e)
       // Create the root finder object, that contains the algorithm
       BisectionRootFinder finder =
              new BisectionRootFinder(new UnaryFunction(f));
       // Define the accuracy you want for the root
       finder.Accuracy = 1.0E-04;
       // Prevent overflow
       finder.Iterations = 30;
       // Compute without bracketing outward
           return finder.Solve(s, e, false);
       catch (Exception ex)
           return FindRoot(0, s - 5, e + 5);
           //this was added letter on to expand the range of start value and end value.

you can call this method from your code using the following code
double temp=RootFinder.FindRoot(0,-1,1);

if you have any problem in using this feel free to comment us.

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Amit Panchal


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