js 计算标准差

var arr = [95,85,75,65,55,45];
function standardDeviation( arr ){
  var avg = 0;
  var length = arr.length; 
  var len = arr.length;
  var sum = 0;
  for(var i = 0; i < len ; i++){
     sum += arr[i];
  }
  avg = sum / len; 
  var temp = [];
  for (var i = 0; i < length; i++) {
   var dev =  (arr[i]) - avg ; //计算数组元素与平均值的差
   temp[i] = Math.pow(dev, 2); //计算差的平方
  }
  var powSum = 0; //用来存储差的平方总和
  for (var j = 0; j < temp.length; j++) {
     if (temp[j]) {
        powSum += temp[j]; //计算差的平方总和
     }
  }
  //用差的平方总和除以数组长度即可得到标准差
  return  parseFloat( Math.sqrt(powSum / length).toFixed(2));

}
standardDeviation(arr);
  

参考： https://www.cnblogs.com/yusuf/p/13055008.html