# Average True Range

ICE Data Services -

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() orinv() [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 statementsvar nValue_0 = xStudy.getValue(0); // Current Bar Index valuevar nValue_1 = xStudy.getValue(-1); // Prior Bar Index valuereturn nValue_0; // Plot Current Bar Index Value}`

Initialize a Series Object based on an external interval:
```var xStudy = null;
var bInit = false; // Initialization flag
function 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 flag
function 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
}```