CODEWITHSUNDEEP
javascriptunderscore.js
Chapsterj
Chapsterj

Reputation: 6625

How to use underscore.js reduce method?

anyone got any examples on how to use the reduce method in underscore.

Upvotes: 2

Views: 14869

Answers (2)

NilColor
NilColor

Reputation: 3542

They have it... http://underscorejs.org/#reduce Right there - at the official Underscore.js site.

Upvotes: 4

kennebec
kennebec

Reputation: 104770

Here are two javascript examples, quite similar to underscore.

These find the mathematical mean and the standard deviation in an array of numbers.

You often see reduce working with thousands or millions of items in arrays related to populatons or statistics.

Math.mean= function(array){
    return array.reduce(function(a, b){return a+b;})/array.length;
}
Math.stDeviation= function(array){
    var mean= Math.mean(array),
    dev= array.map(function(itm){return (itm-mean)*(itm-mean);});
    return Math.sqrt(dev.reduce(function(a, b){return a+b;})/array.length);
}

var A2= [6.2, 5, 4.5, 6, 6, 6.9, 6.4, 7.5];
alert ('mean: '+Math.mean(A2)+'; deviation: '+Math.stDeviation(A2))

/*  returned value: (String)
mean: 6.0625; deviation: 0.899913190257816
*/

Upvotes: 19

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