This is a javascript library for Akima spline interpolation.

Given a set of points in 2D space this library will interpolate a spline (curved line) which often seems more natural than the result from the more common natural cubic spline interpolation.

This is a port of Java code from the Apache Commons Math library, with a bit of code borrowed from the commons-math-interpolation TypeScript port.

Usage

  import Akima from 'akima-interpolator';
  var akima = new Akima();

  var xvals = [
    10,
    20,
    30,
    40,
    50,
    60,
    70,
    80
  ];

  var yvals = [
    40,
    10,
    17,
    39,
    99,
    120,
    30,
    10    
  ];
  
  var f = akima.createInterpolator(xvals, yvals);

  for(var i=xvals[0]; i < xvals[xvals.length-1]; i++) {
    console.log('x:', i, 'y:', f(i));
  }  

Visual example

Christian d'Heureuse has a nice visual demo of his TypeScript port comparing different interpolations here.

Try to put two points very close to each-other on the x-axis but with differing y-axis values, then put a third point far away on the x-axis but close to the second point on the y-axis. Switch between Natural and Akima to see the difference.

License and copyright

This project is licensed under the AGPLv3 license. A copy of the AGPLv3 license is included in the file LICENSE.txt.

This product includes software developed at The Apache Software Foundation (www.apache.org) which is licensed under the Apache 2 License. A copye of the Apache 2 License is included in the file LICENSE_APACHE.txt.

This project includes code ported from the MIT-licensed commons-math-interpolation library. A copy of the MIT License is included in the file LICENSE_MIT.md.

• Copyright 2019 Marc Juul marc@juul.io
• Copyright 2017-2019 Christian d'Heureuse chdh@inventec.ch
• Copyright 2001-2019 The Apache Software Foundation