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

Changelog

v1.0.1

July 1, 2017. Support for Node v0.12, v4, v5, v6, v7, and v8.

v1.0.0

June 24, 2017. First release.