Standard deviation javascript

I think the (main) problem is on this line:

v1 = parseFloat(Math.pow(temp[i]-mean),2);

Should be:

v1 = Math.pow(parseFloat(temp[i])-mean),2);

Your code is trying to use the string in temp[i] as a number and subtract mean from it, and then square it, and then parse the resulting value. Need to parseFloat before using it in a calculation. Also you've got the ,2 outside the closing parenenthesis for the Math.pow call so the squaring won't work either.

Would be helpful to use more meaningful variable names too, I mean, e.g., you have a variable called "square" that holds the result of a square-root operation.

P.S. You need to add some error checking in case the user enters non-numeric data. Check that the result of parseFloat() is not NaN. I'd be inclined to do an initial loop through the array parsing and checking for valid numbers, storing the parsed numbers in a second array (or writing them back to the first array), and if any are invalid give the user an error message at that point and stop. Then in your actual calculations you don't have to worry about parsing as you go (or, in your case, parsing again in the second loop).

Shorthand method for getting standard deviation from an array if you don't like lots of code:

function getStandardDeviation (array) {
  const n = array.length
  const mean = array.reduce((a, b) => a + b) / n
  return Math.sqrt(array.map(x => Math.pow(x - mean, 2)).reduce((a, b) => a + b) / n)
}

For anyone looking for a more generic solution, here's a standard deviation function added to the Array#. The function expects to be called on an array of numbers.

Array.prototype.stanDeviate = function(){
   var i,j,total = 0, mean = 0, diffSqredArr = [];
   for(i=0;i<this.length;i+=1){
       total+=this[i];
   }
   mean = total/this.length;
   for(j=0;j<this.length;j+=1){
       diffSqredArr.push(Math.pow((this[j]-mean),2));
   }
   return (Math.sqrt(diffSqredArr.reduce(function(firstEl, nextEl){
            return firstEl + nextEl;
          })/this.length));
};