Thermostat

Track an infinite curve of values given their inflection points. Or just program a thermostat.

Thermostat represents an infinite function, ƒ(d) = ?, where d is a Date or Number, and ƒ(d) returns a Number, interpolating between all of the points previously added to that function. As I'm not really a math person (honest), I'll show you what I mean with an example.

Imagine the following curve repeats infinitely (each A is the same as the last):

1         C---D
         /     \
0   A---B       A'--

If you query a random point on this curve, it should give you a value between 0 and 1. That said, Thermostat (in an attempt to represent this curve as a function) only cares about A, B, C, and D (and how they repeat).

API

As usual, Thermostat can be included like so:

var thermostat = require('thermostat')

thermostat.lerp(p1, p2, x)

The simple lerp implementation core to the inner-workings of Thermostat, provided for convenience. p1 and p2 are Points (Objects with x and y Numbers), returning the Number result of linearly interpolating between those two points, to x.

curve = thermostat.createCurve(options)

Returns a new Curve instance with the provided options Object. The available options are:

• period: Optional. The period of the curve. Set to 0 to disable repetition. Defaults to the number of milliseconds in one week.
• points: Optional. An Array of { "x": Number|Date|String, "y": Number } pairs, each of which represents a single point on the curve at x with the value y. Defaults to the empty set which, while valid, isn't very interesting: each request returns 0.

y = curve(x)

Returns the Number value of the curve at x, represented as a Date, Number, or String.

A note on inputs

All x values can be either Dates, Numbers, or Strings, treated as follows:

• Number: Used as-is.
• Date: Coerced to a Number as defined by Date.valueOf()
• String: Parsed as a Date, then coerced to a Number likewise.