---
title: RollingStd
---

`RollingStd` calculates a window-based rolling standard deviation in an [`updateBy`](./updateBy.md) table operation. The rolling standard deviation can be calculated using forward and/or backward windows.

## Syntax

```
RollingStd(revTicks, fwdTicks, pairs...)
RollingStd(revTicks, pairs...)
RollingStd(timestampCol, revTime, fwdTime, pairs...)
RollingStd(timestampCol, revTime, pairs...)
RollingStd(timestampCol, revDuration, pairs...)
RollingStd(timestampCol, revDuration, fwdDuration, pairs...)
```

## Parameters

<ParamTable>
<Param name="revTicks" type="long">

The look-behind window size in ticks (rows). If positive, it defines the maximum number of rows _before_ the current row that will be used. If negative, it defines the minimum number of rows _after_ the current row that will be used.

</Param>
<Param name="fwdTicks" type="long">

The look-forward window size in ticks (rows). If positive, it defines the maximum number of rows _after_ the current row that will be used. If negative, it defines the minimum number of rows _before_ the current row that will be used.

</Param>
<Param name="pairs" type="String...">

The input/output column name pairs.

</Param>
<Param name="timestampCol" type="String">

The name of the timestamp column.

</Param>
<Param name="revDuration" type="Duration">

The look-behind window size in Duration.

</Param>
<Param name="fwdDuration" type="Duration">

The look-forward window size in Duration.

</Param>
<Param name="revTime" type="long">

The look-behind window size in nanoseconds.

</Param>
<Param name="fwdTime" type="long">

The look-forward window size in nanoseconds.

</Param>
</ParamTable>

## Returns

An [`UpdateByOperation`](./updateBy.md#parameters) to be used in an [`updateBy`](./updateBy.md) table operation.

## Examples

The following example performs an [`updateBy`](./updateBy.md) on the `source` table using four row-based `RollingStd` operations. Each operation uses different `revTicks` and `fwdTicks` values to show how they affect the output. Note that the first operation only uses `revTicks`.

```groovy order=source,result
rng = new Random()

source = emptyTable(10).update("X = rng.nextInt(25)")

opRollStd = RollingStd(3, "RollingStd = X")
opPrior = RollingStd(3, -1, "WindowPrior = X")
opPosterior = RollingStd(-1, 3, "WindowPosterior = X")
opMiddle = RollingStd(1, 1, "WindowMiddle = X")

result = source.updateBy([opRollStd, opPrior, opPosterior, opMiddle])
```

## Related documentation

- [How to create an empty table](../../../how-to-guides/new-and-empty-table.md#emptytable)
- [How to use `updateBy`](../../../how-to-guides/rolling-aggregations.md)
- [ternary conditional operator](../../../how-to-guides/ternary-if-how-to.md)
- [`update`](../select/update.md)
- [`updateBy`](./updateBy.md)
- [Javadoc](https://deephaven.io/core/javadoc/io/deephaven/api/updateby/UpdateByOperation.html#RollingStd(long,long,java.lang.String...))