Quantile
Computes a quantile for a numeric array.
This module determines the nearest rank and returns the array
value corresponding to that rank.
This module does not currently support multiple interpolation methods, and instead uses a standard elementary method for estimating the quantile.
Installation
$ npm install compute-quantile
For use in the browser, use browserify.
Usage
To use the module,
var quantile = ;
quantile( arr, p[, opts] )
Given a probability 0 <= p <= 1
, computes the quantile for an input array
.
var unsorted = 4 3 5 1 2 ;var q = ;// returns 2
If the input array
is already sorted in ascending order, you can set the sorted
option to true
.
var sorted = 1 2 3 4 5 ;var q = ;// returns 2
Examples
var quantile = ;// Simulate some data...var data = 1000 ;for var i = 0 len = datalength; i < len; i++data i = Math;// Compute the p-quantile for p = 0.5 (median):console;
To run the example code from the top-level application directory,
$ node ./examples/index.js
Notes
The probability p
is equal to k / q
, where q
is the total number of quantiles and k
is the k th quantile.
If the input array
is not sorted in ascending order, the function is O( N log(N) )
, where N
is the input array
length. If the array
is sorted, the function is O(1)
.
Tests
Unit
Unit tests use the Mocha test framework with Chai assertions. To run the tests, execute the following command in the top-level application directory:
$ make test
All new feature development should have corresponding unit tests to validate correct functionality.
Test Coverage
This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:
$ make test-cov
Istanbul creates a ./reports/coverage
directory. To access an HTML version of the report,
$ make view-cov
License
Copyright
Copyright © 2014. Athan Reines.