stats-accumulator

A simple tool for calculating incremental stats on numeric streams. Forked from stats-incremental for minimal memory and maximum portability.

npm install stats-accumulator

E.g. given a source of numbers of unknown length that you would like to at any given time know any of:

• count
• min
• max
• sum
• variance
• stddev

This module can be used either with Node streams via a wrapper such as through2 or without being streaming.

Example

Non-streaming:

var Stats = require('stats-accumulator');

var s = new Stats();

for (var i = 1; i <= 6; i++) s.update(i);

/* E.g.
  { n: 6,
  min: 1,
  max: 6,
  sum: 21,
  mean: 3.5,
  variance: 2.9166666666666665,
  stddev: 1.707825127659933 }
*/

console.log(s.mean);
console.log(s.stddev());

With streams:

var spigot = require('stream-spigot');
var through2 = require('through2');
var terminus = require('terminus');

var Stats = require('stats-accumulator');
var s = new Stats();

var statStream = through2.obj(function (chunk, encoding, callback) {
  s.update(chunk);
  if (s.n % 100000 === 0) {
    console.log(s.toJSON());
  }
  this.push(chunk);
  callback();
});

spigot
  .sync({ objectMode: true }, Math.random)
  .pipe(statStream)
  .pipe(terminus.devnull({ objectMode: true }));

// Prints a stats object each time the stream reaches another 100,000 values.

API

const Stats = require("stats-accumulator")

var stats = new Stats()

Create a new incremental stats aggregator.

stats.update(value)

Update the aggregator with a value. Converted to a Number via parseFloat. If this results in NaN the update is skipped.

stats.toJSON()

Get a up-to-date clone of all of the stats stored.

E.g.

{ n: 97,
  min: 2,
  max: 12,
  sum: 673,
  mean: 6.938144329896907,
  variance: 5.851843979168881,
  stddev: 2.419058490233107 }

stats.n

The count of observations.

stats.min

The min value observed.

stats.max

The max value observed.

stats.sum

The sum of all values observed.

stats.mean

The arithmetic mean of the observations.

stats.variance()

The variance from the mean.

stats.stddev()

The standard deviation of the values from the mean.

Alternatives

stats-lite Operates on complete sets of numbers.

stream-statistics Is a similar module dedicated to streams.

stats-incremental Is the original module, but it accumulates a moving average.

LICENSE

MIT