Rate of Change – EFS

roc() Built-in Study Functions

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 or sym() or inv()	[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
}