https://github.com/noracodes/nrfind

Newton-Raphson root finder for arbitrary differentiable functions
https://github.com/noracodes/nrfind

Last synced: 8 months ago
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Newton-Raphson root finder for arbitrary differentiable functions

• Host: GitHub
• URL: https://github.com/noracodes/nrfind
• Owner: NoraCodes
• License: mit
• Created: 2017-01-11T16:48:07.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2020-01-31T00:03:28.000Z (over 6 years ago)
• Last Synced: 2025-04-09T19:44:04.548Z (over 1 year ago)
• Language: Rust
• Size: 17.6 KB
• Stars: 9
• Watchers: 1
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# nrfind

[![Crates.io version badge](https://img.shields.io/crates/v/nrfind.svg)](https://crates.io/crates/nrfind) [![Build Status](https://travis-ci.org/LeoTindall/nrfind.svg?branch=master)](https://travis-ci.org/LeoTindall/nrfind) ![Passively Maintained](https://img.shields.io/badge/maintenance-passively--maintained-yellowgreen.svg)

`nrfind` provides a Newton-Raphson root finder for arbitrary differentiable functions, as well as convenient wrappers for common use cases like square roots.

Documentation is available on [docs.rs](https://docs.rs/nrfind)

A simple example of usage to find the roots of x^3 + x^2 + 1 in 18 iterations:

```rust

extern crate nrfind;

// The function for whose roots find_root will solve

fn f(x: f64) -> f64 {

    x.powi(3) + x.powi(2) + 1.0

}

// That function's derivative

fn fd(x: f64) -> f64 {

    (3.0 * x.powi(2)) + (2.0 * x)

}

fn main() {

    let initial_guess = 100.0;

    let precision = 0.1;

    let iterations = 18;

    println!("x^3 + x^2 + 1 = 0 when x ~= {}",

             nrfind::find_root(&f, &fd, 

                               initial_guess, 

                               precision, 

                               iterations).unwrap());

}

```

This will print: `x^3 + x^2 + 1 = 0 when x ~= -1.4675327346575013`.

Note that while this method is guaranteed to approximate _a_ root, it may not be

the root you care about! Changing the given `x0` guess can have an impact on 

which root is approximated.