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# Volume Rate of Change (VROC)

## Description

Volume Rate of Change is identical to [Price Rate Of Change (ROC)](/developer/desktop-sdk/references/common/system-indicator-methods/rate-of-change-roc) indicator except that it uses volume instead of price.

## Syntax

`VROC(int period, int smooth)`

`VROC(ISeries\<double\> input, int period, int smooth)`

**Returns default value**

`VROC(int period, int smooth)[int barsAgo]`

`VROC(ISeries\<double\> input, int period, int smooth] (int barsAgo)`

## Return Value

**double**; Accessing this method via an index value `[int barsAgo]` returns the indicator value of the referenced bar.

## Parameters

| Parameter | Description                                                                                     |
| --------- | ----------------------------------------------------------------------------------------------- |
| input     | Indicator source data ([Series\<T>](/developer/desktop-sdk/references/common/iseriest/seriest)) |
| period    | Number of bars used in the calculation                                                          |
| smooth    | The number of bars for smoothing the signal                                                     |

## Example

```csharp
// Prints the current value of VROC  
double value = VROC(13, 3)[0];  
Print("The current VROC value is " + value.ToString());
```

## Source Code

You can view this indicator method source code by selecting the menu New > NinjaScript Editor > Indicators within the NinjaTrader Control Center window.