170 lines
3.5 KiB
Markdown
170 lines
3.5 KiB
Markdown
stats-incremental
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=====
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[](https://nodei.co/npm/stats-incremental/)
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A light statstical package for incremental (i.e. rolling, streaming) sets of numbers.
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E.g. given a source of numbers of unknown length that you would like to at any given time know any of:
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* count
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* min
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* max
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* sum
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* variance
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* standard_deviation
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* simple moving average
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This module can be used either with Node `streams` via a wrapper such as `through2` or without being streaming.
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Example
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---
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Non-streaming:
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```javascript
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var Stats = require("stats-incremental")
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var dice = require("dice")
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var s = Stats()
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var rolls = []
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for (var i = 0; i < 100; i++) {
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s.update(dice.sum(dice.roll("2d6")))
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console.log(s.getAll())
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}
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/* E.g.
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{ n: 97,
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min: 2,
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max: 12,
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sum: 673,
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mean: 6.938144329896907,
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variance: 5.851843979168881,
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standard_deviation: 2.419058490233107,
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sma50: 6.82 }
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*/
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console.log(s.mean)
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console.log(s.standard_deviation)
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```
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With streams:
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```js
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var spigot = require("stream-spigot")
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var through2 = require("through2")
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var terminus = require("terminus")
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var Stats = require("stats-incremental")
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var s = Stats()
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var statStream = through2.obj(function (chunk, encoding, callback) {
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s.update(chunk)
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if (s.n % 100000 === 0) {
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console.log(s.getAll())
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}
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this.push(chunk)
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callback()
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})
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spigot.sync({objectMode: true}, Math.random)
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.pipe(statStream)
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.pipe(terminus.devnull({objectMode: true}))
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/*
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{ n: 100000,
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min: 2.0884908735752106e-7,
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max: 0.9999937505926937,
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sum: 49861.06196602131,
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mean: 0.49861061966021336,
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variance: 0.08331362954827709,
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standard_deviation: 0.28864100462040576,
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sma50: 0.5422519558777934 }
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{ n: 200000,
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min: 2.0884908735752106e-7,
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max: 0.9999937505926937,
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sum: 99904.73041411326,
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mean: 0.49952365207056687,
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variance: 0.08316120223669865,
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standard_deviation: 0.2883768406732736,
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sma50: 0.4396136475716979 }
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*/
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```
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API
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===
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## `const Stats = require("stats-incremental")`
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## `var stats = new Stats(smaBins)`
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Create a new incremental stats aggregator. The `smaBins` argument is optional (default 50) and will choose the size of recent window to retain to calculate the Simple Moving Average on the recent data.
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## `stats.update(value)`
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Update the aggregator with a value. Converted to a Number via parseFloat. If this results in NaN the update is skipped.
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## `stats.getAll()`
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Get a up-to-date clone of all of the stats stored.
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E.g.
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```js
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{ n: 97,
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min: 2,
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max: 12,
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sum: 673,
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mean: 6.938144329896907,
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variance: 5.851843979168881,
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standard_deviation: 2.419058490233107,
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sma50: 6.82 }
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```
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## `stats.n`
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The count of observations.
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## `stats.min`
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The min value observed.
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## `stats.max`
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The max value observed.
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## `stats.sum`
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The sum of all values observed.
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## `stats.mean`
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The arithmetic mean of the observations.
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## `stats.variance`
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The variance from the mean.
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## `stats.standard_deviation`
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The standard deviation of the values from the mean.
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## `stats.smaXX`
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Get the Simple Moving Average of the recent data. Default is to store 50 recent records and expose an `sma50` property with the simple moving average. If the `Stats` object is created with an argument of a number of SMA bins, the property will reflect the number of bins, e.g. `Stats(100)` will have an `sma100` instead of `sma50` property.
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Alternatives
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---
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[stats-lite](http://npm.im/stats-lite) Operates on complete sets of numbers.
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[stream-statistics](http://npm.im/stream-statistics) Is a similar module dedicated to streams.
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LICENSE
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=======
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MIT
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