envelope Auto Percentage

[bark]

How can I create an envelope (EMA Channel) that the Percentage will be calculated automatically as follow: (standard deviation of last 100 days) / (last price) *100

I already have the formula to calculate the Percentage, but I cen`t combine it to the envelop formula

thanks in advance for the help

the (standard deviation of last 100 days) / (last price) *100 formula:

/*********************************

var nStdev = callFunction("StandardDeviation.efs", "main", 10, "Close");

if (nStdev == null) return;

********************************/





function preMain() {

setStudyTitle("Envelop per");

setDefaultBarFgColor(Color.RGB(192,87,255));

setCursorLabelName("Env per");

}



function main(nLength, sPriceSource) {

if (nLength == null) nLength = 100;

if (sPriceSource == null) sPriceSource = "Close";



var aSource = getValue(sPriceSource, 0, -nLength);

if (aSource == null) return null;






var sumX = 0;

var sumX2 = 0;

for (i = 0; i < nLength; ++i) {

sumX += aSource[i];

sumX2 += (aSource[i] * aSource[i])

}

var meanX = (sumX/nLength);
varClose = getValue("Close")



var stdev = Math.sqrt((sumX2/nLength) - (meanX*meanX))/close(-1)*100 ;



return stdev;

}

[ACM]

Re: envelope Auto Percentage

bark
In the formula in which you compute the envelope use the efsExternal() function to call the efs that computes the Standard Deviation and then use the value returned by that call in your calculations of the envelope.
For the description and syntax of the efsExternal() function see this article in the EFS KnowledgeBase. You can find additional detailed examples in this thread on the efsInternal() and efsExternal() functions and in this thread that provides more examples on how to create studies on studies using these functions
Alex

Originally posted by bark
How can I create an envelope (EMA Channel) that the Percentage will be calculated automatically as follow: (standard deviation of last 100 days) / (last price) *100

I already have the formula to calculate the Percentage, but I cen`t combine it to the envelop formula

thanks in advance for the help

the (standard deviation of last 100 days) / (last price) *100 formula:

/*********************************

var nStdev = callFunction("StandardDeviation.efs", "main", 10, "Close");

if (nStdev == null) return;

********************************/





function preMain() {

setStudyTitle("Envelop per");

setDefaultBarFgColor(Color.RGB(192,87,255));

setCursorLabelName("Env per");

}



function main(nLength, sPriceSource) {

if (nLength == null) nLength = 100;

if (sPriceSource == null) sPriceSource = "Close";



var aSource = getValue(sPriceSource, 0, -nLength);

if (aSource == null) return null;






var sumX = 0;

var sumX2 = 0;

for (i = 0; i < nLength; ++i) {

sumX += aSource[i];

sumX2 += (aSource[i] * aSource[i])

}

var meanX = (sumX/nLength);
varClose = getValue("Close")



var stdev = Math.sqrt((sumX2/nLength) - (meanX*meanX))/close(-1)*100 ;



return stdev;

}