Exponential Moving Averages

[Gene]

I would be extremely greatful if someone would explain to me EXACTLY how to calculate exponential moving averages EXACTLY the same way esignal does. I have found several different formulas in various books but none of them produce the exact same results as are produced by esignal.

Thanks !

[GenSpoo]

This works for me and gives me the same line as the builtin study.

function main(nPeriod) {
if (nPeriod == null) nPeriod = 20;

var x1 = 2 / (nPeriod + 1);
var x2 = 1 - x1;

return (x1 * close()) + (x2 * ref(-1));
}

[GenSpoo]

Actually, I guess that should be altered a bit so that it deals with the first bars in the series better. I'm using ref() here, but you could store that previous value in a variable or other such method.

function main(nPeriod) {
if (nPeriod == null) nPeriod = 20;

var x1 = 2 / (nPeriod + 1);
var x2 = 1 - x1;
var prevVal = ref(-1) == null ? close() : ref(-1);

return (x1 * close()) + (x2 * prevVal);
}