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calculate

This is the main callback function where all calculations for the custom study are performed and its results are updated.

Syntax

calculate(beginIndex, endIndex);

Parameters

beginIndex

Numeric value that indicates the beginning position of the data range for which the study needs to calculate new values.

endIndex

Numeric value that indicates the ending position of the data range for which the study needs to calculate new values.

Remarks

When ActiveTick needs to update study's contents, it calls this callback function with the range for which it needs the new calculations. This usually happens in the following scenarios:

When internal chart data is reloaded, beginIndex and endIndex represent the range for an entire chart dataset
When the underlying value of the data source or OHLCV data is changed, beginIndex and endIndex represent the range of 1, or minRequiredDataValue set with setMinRequiredDataValues() method.
When a new trade message is received from the server.

calculate() callback function should process only what is being asked of it by beginIndex and endIndex, and all appropriate StudyData should be inserted or updated.

Example

The following example demonstrates calculate() callback function.

function init()

{

//setup study's initial settings

this.setName("cSMA");

this.addDataPlot("customSMA");

this.addParameter("Period", 10);

//set to true so that this study can use *any* data source

setAnyDataSource(true);

//moving average requires a minimum of periods to calculate one value

setMinRequiredDataValues(this.getParameter("Period"));

}

function calculate(beginIndex, endIndex)

{

//retrieve current period value

var period = parseInt(this.getParameter("Period"));

//retrieve enough data from the source to satisfy ActiveTick's request to calculate values for begin-end range

var sourceDataArray = this.getSourceData(beginIndex, endIndex);

//retrieve previously calculated data

var studyData = this.getStudyData("customSMA");

//calculate moving average array

var maArray = customSMA(sourceDataArray, period);

//populate studyData with our results

var dataIndex = maArray.length - 1;

for(var i = endIndex - 1; i >= beginIndex; i--)

{

if(dataIndex >= 0)

studyData.set(i, maArray[dataIndex--]);

else

{

//set null value for current i so that ActiveTick doesn't draw any at current i

studyData.set(i, null);

}

function customSMA(data, period)

{

//calculate moving average given an array of data points and Period value

var ma = new Array();

var maCount = 0;

for(var i = 0; i <= data.length - period; i++)

{

var totalPrices = 0;

var pricesCount = 0;

for(j = i; j < i + period; j++)

{

totalPrices += data[j];

pricesCount++;

}

ma[maCount] = (totalPrices / pricesCount);

maCount++;

}

return ma;

}