stats-lite - npm Package Compare versions

Comparing version 2.1.1 to 2.2.0

package.json

 {
   "name": "stats-lite",
-  "version": "2.1.1",
+  "version": "2.2.0",
   "description": "A light statistical package that operates on numeric Arrays.",
@@ -5,0 +5,0 @@ "main": "stats.js",

README.md

@@ -35,14 +35,16 @@ stats-lite
 console.log("standard deviation: %s", stats.stdev(rolls))
+console.log("sample standard deviation: %s", stats.sampleStdev(rolls))
 console.log("85th percentile: %s", stats.percentile(rolls, 0.85))
-console.log("histogram:", stats.histogram(rolls))
+console.log("histogram:", stats.histogram(rolls, 10))
 
 /* Your exact numbers may vary, but they should be pretty similar:
-sum: 21006
-mean: 7.002
+sum: 21041
+mean: 7.0136666666666665
 median: 7
 mode: 7
-variance: 5.907329333333325
-standard deviation: 2.430499811424252
+variance: 5.8568132222220415
+standard deviation: 2.4200853749861886
+sample standard deviation: 2.4204888234135953
 85th percentile: 10
-histogram { values: [ 86, 159, 253, 335, 907, 405, 339, 270, 146, 100 ],
+histogram { values: [ 94, 163, 212, 357, 925, 406, 330, 264, 164, 85 ],
   bins: 10,
@@ -99,3 +101,3 @@ binWidth: 1.05,
 
-Calculate the [variance](http://en.wikipedia.org/wiki/Variance) from the mean.
+Calculate the [variance](http://en.wikipedia.org/wiki/Variance) from the mean for a population.
 
@@ -105,4 +107,15 @@ `stdev(vals)`
 
-Calculate the [standard deviation](http://en.wikipedia.org/wiki/Standard_deviation) of the values from the mean.
+Calculate the [standard deviation](http://en.wikipedia.org/wiki/Standard_deviation) of the values from the mean for a population.
 
+`sampleVariance(vals)`
+---
+
+Calculate the [variance](http://en.wikipedia.org/wiki/Variance) from the mean for a sample.
+
+`sampleStdev(vals)`
+---
+
+Calculate the [standard deviation](http://en.wikipedia.org/wiki/Standard_deviation) of the values from the mean for a sample.
+
+
 `percentile(vals, ptile)`
@@ -109,0 +122,0 @@ ---

stats.js

@@ -8,4 +8,8 @@ "use strict";
 module.exports.mode = mode
-module.exports.variance = variance
-module.exports.stdev = stdev
+module.exports.variance = populationVariance
+module.exports.sampleVariance = sampleVariance
+module.exports.populationVariance = populationVariance
+module.exports.stdev = populationStdev
+module.exports.sampleStdev = sampleStdev
+module.exports.populationStdev = populationStdev
 module.exports.percentile = percentile
@@ -102,4 +106,6 @@ module.exports.histogram = histogram
 
-// Variance = average squared deviation from mean
-function variance(vals) {
+// This helper finds the mean of all the values, then squares the difference
+// from the mean for each value and returns the resulting array.  This is the
+// core of the varience functions - the difference being dividing by N or N-1.
+function valuesMinusMeanSquared(vals) {
   vals = numbers(vals)
@@ -111,10 +117,29 @@ var avg = mean(vals)
   }
-  return mean(diffs)
+  return diffs
 }
 
-// Standard Deviation = sqrt of variance
-function stdev(vals) {
-  return Math.sqrt(variance(vals))
+// Population Variance = average squared deviation from mean
+function populationVariance(vals) {
+  return mean(valuesMinusMeanSquared(vals))
 }
 
+// Sample Variance
+function sampleVariance(vals) {
+  var diffs = valuesMinusMeanSquared(vals)
+  if (diffs.length <= 1) return NaN
+
+  return sum(diffs) / (diffs.length - 1)
+}
+
+
+// Population Standard Deviation = sqrt of population variance
+function populationStdev(vals) {
+  return Math.sqrt(populationVariance(vals))
+}
+
+// Sample Standard Deviation = sqrt of sample variance
+function sampleStdev(vals) {
+  return Math.sqrt(sampleVariance(vals))
+}
+
 function percentile(vals, ptile) {
@@ -121,0 +146,0 @@ vals = numbers(vals)

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Improved metrics

Total package byte prevSize

11311

increased by13.4%

Lines of code

182

increased by12.35%

Number of lines in readme file

141

increased by10.16%

No dependency changes