# Rate of Change

ICE Data Services -

The Rate-of-Change (ROC) indicator displays the difference between the current price and the price x time periods ago. The difference can be displayed either in points or as a percentage. The momentum indicator displays the same information but expresses it as a ratio.

Syntax

roc( nLength [, Series | sym() | inv() ][, nBarIndex ] )

Parameters

 Parameter: Description: Default: nLength Required. Number of periods to use for calculation. n/a Series orsym() orinv() [Optional]  Series Object or 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 roc(10);
}

Single Line Study-on-Study Indicator:
function main() {
return roc(10, hl2());
}

Retrieve single values:

function main() {
var nValue_0 = roc(10, 0); // Current Bar Index
var nValue_1 = roc(10, -1); // Prior Bar Index
return new Array(nValue_0, nValue_1);
}

Initialize a Series Object:

var xStudy = null;
function main() {
if (xStudy == null) {
xStudy = roc(10);
} // 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 flag
function main() {
if (bInit == false) {
xStudy = roc(10, 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 = roc(10, 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
}