Does an efs exist to create a Std. Dev series from another series?

[jgr]

I would like to create standard deviation bands around another series. Does anyone know of a function to do that already available?

[geme]

// ------------------------------------
// Get a StdDev value
// Parameters:
//   aSerie  = Series Object
//   nLength = Length of StdDev
// ------------------------------------
function getStdDev(aSerie, nLength) {
    // get average
    var vsma = sma(nLength,aSerie).getValue(0);
    // Compute the numerator inside the square root
    var sum = 0;
    for (i=0; i<nLength; i++) {
      sum += Math.pow((aSerie.getValue(-i)-vsma), 2);
    }
    var numerator = sum;
    // Compute the denominator
    var denominator = i - 1;
    // Compute the value inside the square root
    var value = numerator / denominator;
    // Take the square root of the value to find the standard deviation
    var stdev = Math.sqrt(value);
    return stdev;
} 

[geme]

Here an example:

[geme]

Apology a mistake is in the Coding.
Would be correct:

StdDev.efs

    return Math.sqrt(sum/nLength); 

Function

    // Compute the denominator
    var denominator = nLength; 

Sorry