Added harmonic mean

README.md

@@ -1,7 +1,7 @@
 Math Stats [![Build Status](https://travis-ci.org/pavanvamsi3/math-stats.svg?branch=sd_and_variance)](https://travis-ci.org/pavanvamsi3/math-stats)  [![Coverage Status](https://coveralls.io/repos/github/pavanvamsi3/math-stats/badge.svg?branch=master)](https://coveralls.io/github/pavanvamsi3/math-stats?branch=master)
 =========
 
-A small library that calculates mean, median and mode for your numbers
+A small library that does statistics for your numbers
 
 ### Installation
 
@@ -20,6 +20,7 @@ var median = stats.median(numbers); // returns 2
 var modes = stats.mode(moreNumbers); // returns [1]
 var standardDeviation = stats.standardDeviation(numbers); // returns 0.816496580927726
 var variance = stats.variance(numbers); // returns 0.6666666666666666
+var harmonicMean = stats.harmonicMean(numbers); returns 1.6363636363636365
 ```
 
 ### Tests

index.js

@@ -71,10 +71,22 @@ let variance = numbers => {
     return variance;
 };
 
+let harmonicMean = numbers => {
+    if (!Array.isArray(numbers)) {
+        return null;
+    }
+    let total = numbers.reduce(function(sum, value) {
+        return sum + (1/value);
+    }, 0);
+
+    return numbers.length/total;
+};
+
 module.exports = {
     mean: mean,
     median: median,
     mode: mode,
     standardDeviation: standardDeviation,
-    variance: variance
+    variance: variance,
+    harmonicMean: harmonicMean
 };

package.json

@@ -1,6 +1,6 @@
 {
   "name": "math-stats",
-  "version": "0.2.5",
+  "version": "0.2.6",
   "description": "Statistics for your numbers",
   "main": "index.js",
   "scripts": {

test/test.js

@@ -35,5 +35,9 @@ describe('#stats', function() {
         result = Object.is(result, NaN);
         expect(result).to.equal(true);
     });
+    it('Harmonic Mean', function() {
+        var result = stats.harmonicMean([1, 2, 3]);
+        expect(result).to.equal(1.6363636363636365);
+    });
 });