# Average True Range

ICE Data Services -

atr() Built-in Study Functions

The Average True Range study (ATR) is a measure of volatility. It was introduced by Welles Wilder in his book New Concepts in Technical Trading Systems and has since been used as a component of many indicators and trading systems. Wilder has found that the high ATR values often occur at market bottoms following a "panic" sell-off. Low ATR values are often found during extended sideways periods, such as those found at tops and after consolidation periods.

Syntax
atr( nLength [, sym() | inv() ][, nBarIndex ] )

Parameters
Parameter: Description: Default:
nLength Required. Number of periods to use for calculation.

n/a sym() or
inv()
[Optional]  Function of sym() or inv() to determine symbol/interval source for the study.

Chart's sym/inv nBarIndex [Optional]  Bar index of series to retrieve.

n/a

Return Value(s)

Returns a Series Object when nBarIndex is not specified.

Returns a single value when nBarIndex is specified.

Notes
Only available in versions 7.9 or later.

Code Examples
Single Line Indicator:
 `function main() { return atr(14);}`

Retrieve single values:
 ``function main() { var nValue_0 = atr(14, 0); // Current Bar Index var nValue_1 = atr(14, -1); // Prior Bar Index return new Array(nValue_0, nValue_1);}``

Initialize a Series Object:
 ``var xStudy = null;function main() { if (xStudy == null) { xStudy = atr(14); } // retrieve single values for conditional statements var nValue_0 = xStudy.getValue(0); // Current Bar Index value var nValue_1 = xStudy.getValue(-1); // Prior Bar Index value return nValue_0; // Plot Current Bar Index Value}``

Initialize a Series Object based on an external interval:
 ``var xStudy = null;var bInit = false; // Initialization flagfunction main() { if (bInit == false) { xStudy = atr(14, inv(20)); // 20-min interval bInit = true; } // retrieve single values for conditional statements var nValue_0 = xStudy.getValue(0); // Current Bar Index value var nValue_1 = xStudy.getValue(-1); // Prior Bar Index value return getSeries(xStudy); // Synchronized Series plot}``

Initialize a Series Object based on an external symbol and interval:
 ``var xStudy = null;var bInit = false; // Initialization flagfunction main() { if (bInit == false) { xStudy = atr(14, sym("IBM,20")); // IBM 20-min interval bInit = true; } // retrieve single values for conditional statements var nValue_0 = xStudy.getValue(0); // Current Bar Index value var nValue_1 = xStudy.getValue(-1); // Prior Bar Index value return getSeries(xStudy); // Synchronized Series plot}``