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statistics - npm Package Compare versions
Comparing version 2.0.1 to 3.0.0
71
index.js
@@ -0,43 +1,40 @@ | ||
| module.exports = function reduce (acc, value) { | ||
| //handle when called without initial | ||
| if('number' === typeof acc) | ||
| return reduce(reduce(null, acc), value) | ||
| //set initial if initial was null | ||
| else if(null == acc) | ||
| return { | ||
| mean: value, | ||
| sum: value, | ||
| sqsum: value*value, | ||
| count: 1, | ||
| stdev: 0 | ||
| } | ||
| // | ||
| // caluclate simple statistics | ||
| // | ||
| var sum = acc.sum + value | ||
| var count = acc.count + 1 | ||
| var sq = value*value | ||
| module.exports = Stats | ||
| var mean = sum/count | ||
| var sqsum = acc.sqsum + sq | ||
| function Stats () { | ||
| if (!(this instanceof Stats)) return new Stats() | ||
| this.sum = 0 | ||
| this.sqsum = 0 | ||
| this.mean = 0 | ||
| this.count = 0 | ||
| this.max = null | ||
| this.min = null | ||
| } | ||
| return { | ||
| //these values useful output | ||
| mean: mean, | ||
| stdev: Math.sqrt(sqsum/count - mean*mean), | ||
| Stats.prototype = { | ||
| value: function (val) { | ||
| this.sum += val | ||
| this.sqsum += val*val | ||
| this.count ++ | ||
| this.mean = this.sum / this.count | ||
| this.max = | ||
| this.max === null ? val | ||
| : val > this.max ? val | ||
| : this.max | ||
| this.min = | ||
| this.min === null ? val | ||
| : val < this.min ? val | ||
| : this.min | ||
| return this | ||
| }, | ||
| get variance () { | ||
| return this.sqsum / this.count - (this.mean * this.mean) | ||
| }, | ||
| get stdev() { | ||
| return Math.sqrt(this.variance) | ||
| }, | ||
| toJSON: function () { | ||
| return {mean: this.mean, count: this.count, stdev: this.stdev} | ||
| //these values needed to maintain state. | ||
| count: count, | ||
| sum: sum, | ||
| sqsum: sqsum | ||
| } | ||
| } | ||
| { | ||
| "name": "statistics", | ||
| "version": "2.0.1", | ||
| "version": "3.0.0", | ||
| "description": "calculate mean standard deviation in one pass", | ||
@@ -5,0 +5,0 @@ "homepage": "http://github.com/dominictarr/statistics", |
| # statistics | ||
| calculate mean and standard deviation in one pass. | ||
| a reduce function that calculates mean and standard deviation in one pass | ||
| I first wrote this module a long long time ago, and i used an object oriented | ||
| api. Today I needed to serialize a stats output to JSON, and then later parse it, | ||
| and keep using it. Continuing to use an OO api would mean a bunch of glue code, | ||
| so I rewrote it as a reduce function. | ||
| ## example | ||
| ``` js | ||
| var Stats = require('statistics') | ||
| var s = Stats() | ||
| var stats = require('statistics') | ||
| s.value(1).value(2).value(3) | ||
| console.log('mean:', s.mean, 'stdev:', s.stdev) | ||
| > mean: 2 stdev: 0.86... | ||
| console.log([1,2,3].reduce(stats)) | ||
| => { | ||
| mean: 2, | ||
| stdev: 0.8164965809277263, | ||
| count: 3, | ||
| sum: 6, | ||
| sqsum: 14 | ||
| } | ||
| ``` | ||
| you probably only want to have the mean and stdev, the other fields are necessary for the reduce | ||
| function however. | ||
| It's possible to output values as you go. | ||
| Since `stdev` is calculated in one pass, | ||
| this has minimal memory commitments so you can take averages of everything. | ||
| ## functional is better than object oriented | ||
| statistics@2 and earlier used an object oriented api, but then I needed to serialize and parse a stats | ||
| object and keep using it. That was incredibly easy with a reduce function, but would have meant | ||
| a bunch of ugly glue code with OO. | ||
| ## LICENSE | ||
| MIT |
| var reduce = require('../') | ||
| var tape = require('tape') | ||
| , Stats = require ('../') | ||
| tape('mean', function (t) { | ||
| tape('statistics as reduce', function (t) { | ||
| var s = Stats() | ||
| s.value(1).value(2) | ||
| t.equal(s.mean, 1.5) | ||
| t.equal(s.min, 1) | ||
| t.equal(s.max, 2) | ||
| t.end() | ||
| var stats = [1,2,3].reduce(reduce) | ||
| }) | ||
| t.deepEqual(stats, { | ||
| mean: 2, | ||
| stdev: Math.sqrt((1*1+2*2+3*3)/3 - 2*2), | ||
| tape('stdev', function (t) { | ||
| sum: 1+2+3, | ||
| count: 3, | ||
| sqsum: 1*1+2*2+3*3 | ||
| }) | ||
| var s = Stats() | ||
| s.value(1).value(2).value(3) | ||
| t.equal(s.mean, 2) | ||
| t.equal(s.min, 1) | ||
| t.equal(s.max, 3) | ||
| //sum of squares | ||
| t.equal(s.sqsum, 1*1+2*2+3*3) | ||
| //calculate stdev: (sqsum/n - mean^2) | ||
| console.log(stats) | ||
| var stdev = Math.sqrt((1*1+2*2+3*3)/3 - 2*2) | ||
| t.equal(s.stdev, stdev) | ||
| t.deepEqual(s.toJSON(), {mean: 2, count: 3, stdev: stdev}) | ||
| t.end() | ||
| }) | ||
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Improved metrics
- Total package byte prevSize
- increased by5.41%
2457
- Number of lines in readme file
- increased by72.73%
38
Worsened metrics
- Lines of code
- decreased by-33.33%
42
No dependency changes