---
id: "M:cAlgo.API.Internals.IIndicatorsAccessor.NegativeVolumeIndex(cAlgo.API.DataSeries)"
kind: "method"
type: "T:cAlgo.API.Internals.IIndicatorsAccessor"
url: "https://help.ctrader.com/ctrader-algo/references/Indicators/IIndicatorsAccessor/NegativeVolumeIndex/"
---

> Documentation index for agents: https://help.ctrader.com/ctrader-algo/llms.txt · machine index: https://help.ctrader.com/ctrader-algo/api.json

# IIndicatorsAccessor.NegativeVolumeIndex

Member of [IIndicatorsAccessor](https://help.ctrader.com/ctrader-algo/references/Indicators/IIndicatorsAccessor/index.md).

## NegativeVolumeIndex(DataSeries source)

The Negative Volume Index is a calculation of the percentage change in price on days when trading volume declines.

Environments: Desktop supported · CLI supported · Cloud supported.

C#:

```csharp
NegativeVolumeIndex NegativeVolumeIndex(DataSeries source)
```

Python:

```python
api.Indicators.NegativeVolumeIndex(source: DataSeries) -> NegativeVolumeIndex
```

### Parameters

- `source` (`DataSeries`, Python `DataSeries`): The price source data used for the calculation.

### Returns

`NegativeVolumeIndex` — Negative Volume Index indicator instance

### Examples

C#:

```csharp
var negativeVolumeIndex = Indicators.NegativeVolumeIndex(Bars.ClosePrices);
Print("Negative Volume Index: {0}", negativeVolumeIndex.Result.LastValue);
```

Python:

```python
negativeVolumeIndex = api.Indicators.NegativeVolumeIndex(api.Bars.ClosePrices)
api.Print(f"Negative Volume Index: {negativeVolumeIndex.Result.LastValue}")
```