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Standard deviation(STDEV) with JavaScript
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var stdev = function(arr) { | |
var n = arr.length; | |
var sum = 0; | |
arr.map(function(data) { | |
sum+=data; | |
}); | |
var mean = sum / n; | |
var variance = 0.0; | |
var v1 = 0.0; | |
var v2 = 0.0; | |
if (n != 1) { | |
for (var i = 0; i<n; i++) { | |
v1 = v1 + (arr[i] - mean) * (arr[i] - mean); | |
v2 = v2 + (arr[i] - mean); | |
} | |
v2 = v2 * v2 / n; | |
variance = (v1 - v2) / (n-1); | |
if (variance < 0) { variance = 0; } | |
stddev = Math.sqrt(variance); | |
} | |
return { | |
mean: Math.round(mean*100)/100, | |
variance: variance, | |
deviation: Math.round(stddev*100)/100 | |
}; | |
}; |
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