interpo

alt="Build status" align="right">

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

Usage

``js
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][scipy-pchip] 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][pchdoc] library.

$3

##### 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!

$3

#### 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

$3

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

$3

June 24, 2017. First release.

[homebrew]: http://brew.sh
[node.js]: http://nodejs.org
[pchdoc]: http://www.netlib.org/slatec/pchip/pchdoc.f
[scipy-pchip]: http://docs.scipy.org/doc/scipy-dev/reference/generated/scipy.interpolate.PchipInterpolator.html
[slatec]: http://www.netlib.org/slatec/