Statistic Module added

docs/underscore.collections.statistics.md

@@ -0,0 +1,151 @@
+### statistics
+
+> Statisctics Functions. <a href="docs/underscore.collections.statistics.js.html" class="btn btn-primary btn-xs">View Annotated Source</a>
+
+#### mean
+
+Signature: `_.mean(... arrays:Array ...)`
+
+The `_.mean` function finds out the average value from the array of numbers.
+
+```javascript
+
+_.mean([]);
+//=> 0
+
+_.mean([0, 1, 2, 3, 4]);
+//=> 2
+
+_.mean(null)
+//=> 0
+
+```
+
+#### median
+
+Signature: `_.median(... arrays:Array ...)`
+
+The `_.median` function finds out the middle value from the array of numbers.
+
+Calulation of median is done using the following method.
+
+If the array has odd numbers then median is the middle element.
+
+If the array has even numbers then average of middle two numbers is the median value.
+```javascript
+
+_.median([]);
+//=> undefined
+
+_.median([1, 2, 3]);
+//=> 2
+
+_.median([1, 2, 3, 4])
+// => 2.5
+
+```
+
+#### sum
+
+Signature: `_.sum(... arrays:Array ...)`
+
+The `_.sum` function calculates the sum of the given arrays.
+
+```javascript
+
+_.sum([]);
+//=> 0
+
+_.sum([0, 1, 2, 3, 4]);
+//=> 10
+```
+
+#### variance
+
+Signature: `_.variance(... arrays:Array ...)`
+
+The `_.variance` function return the variance of the numeric elements of the collection.
+
+```javascript
+
+_.variance([]);
+//=> 0
+
+_.variance([0, 1, 2, 3, 4]);
+//=> 1.25
+```
+
+#### standardDeviation
+
+Signature: `_.standardDeviation(... arrays:Array ...)`
+
+The `_.standardDeviation` function return the standard deviation of the numeric elements of the collection.
+
+```javascript
+
+_.standardDeviation([]);
+//=> 0
+
+_.standardDeviation([1, 2, 3, 4]);
+//=> 1.118
+```
+
+#### standardError
+
+Signature: `_.standardError(... arrays:Array ...)`
+
+The `_.standardError` function return the standard error of the numeric elements of the collection.
+
+```javascript
+
+_.standardError([]);
+//=> 0
+
+_.standardError([1, 2, 3, 4]);
+//=> 0.64
+```
+
+#### mode
+
+Signature: `_.mode(... arrays:Array ...)`
+
+The `_.mode` function return the element (or element-based computation) that appears most frequently in the collection.
+
+```javascript
+
+_.mode([]);
+//=> undefined
+
+_.mode([1, 1, 3, 4]);
+//=> 1
+```
+
+#### statRange
+
+Signature: `_.statRange(... arrays:Array ...)`
+
+The `_.statRange` function return the difference of the max and min value of the elements in the array.
+
+```javascript
+
+_.statRange([]);
+//=> -Infinity
+
+_.statRange([1, 1, 3, 4]);
+//=> 3
+```
+
+#### percentile
+
+Signature: `_.percentile(... arrays:Array ...,percentileval:number)`
+
+The `_.percentile` function return the percentile value of the numeric elements from the collection like 50th,75th,99th etc.
+
+```javascript
+
+_.percentile([], 10);
+//=> 0
+
+_.percentile([1, 1, 3, 4], 50);
+//=> 2
+```

modules/variance.js

@@ -9,7 +9,7 @@ export default function variance(collection, iteratee, context) {
   if (typeof iteratee == 'number' && collection != null && typeof collection[0] != 'object') { 
     iteratee = null;
   }
-  iteratee = cb(iteratee, context);
+  iteratee = iteratee(iteratee, context);
 
   var computed = [];
   var avg = mean(collection, function(value, key, collection) {