Notice: This repository is no longer maintained as of 3/26/2024

interpo

Piecewise cubic hermite spline interpolating polynomials (pchips) for Node.js.

Usage

var interpo = require("interpo");

var pchip = new interpo.Pchip(
  [1, 2,  3,  4,  5],
  [1, 7, 11, 14, 28]);

pchip.evaluate(3);   // 11
pchip.evaluate(4.2); // 15.464470588

Details

Interpolates known data points with a monotonic cubic spline.

See scipy's PchipInterpolator for mathematical details. Note that interpo does not use scipy's algorithm—you may observe slight differences between scipy's interpolants and ours. We instead link against the SLATEC PCHIP library.

API

`new interpo.Pchip(x, f)`

Creates a new PchipInterpolator approximating some function f(x) defined by the given data points.

x numeric array
an array of strictly increasing x values for the known data points
f numeric array
an array of f(x) values for the known data points

`PchipInterpolator#evaluate(x)`

x numeric
an x value at which to evaluate the interpolant

Installation

npm install interpo

interpo links against an ancient Fortran mathematical library, SLATEC. You'll need GNU Fortran installed to compile this module.

Other Fortran compilers are not supported at this time. PRs welcome!

GNU Fortran

Debian/Ubuntu

Just install the gfortran package and you're good to go:

sudo apt-get install gfortran

OS X

You'll need to get a version of gfortran that matches the version of your gcc. The easiest way to do this is to use Homebrew to replace your entire GCC stack:

brew install gcc
brew link --force gcc

Interpo

Install / Use

README