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Ranks the slope of a pair of vectors through the origin in clockwise order. This is more robust than comparing their arc tangents using atan2.


First install using npm:

npm install compare-slope

Then use as follows:

var compareSlope = require("compare-slope")
console.log(compareSlope([0, 1], [1, 2]))

require("compare-slope")(a, b)

Checks whether a comes before b in a counter-clockwise ordering.

  • a and b are both represented by arrays of at least length 2


  • > 0 if b is clockwise from a
  • < 0 if a is clockwise from b
  • 0 if a and b are collinear

Note: Somewhat arbitrarily, the degenerate point at the origin is ranked before all other points.


(c) 2013 Mikola Lysenko. MIT License