# Variable Index Dynamic Average

## Description

The Variable Index Dynamic Average indicator modifies the Exponential Moving Average by varying the smoothness based on recent volatility.

It takes three parameters: a short period n, a long period m, and a smoothing factor a. a is usually 0.2.

It is built up using a ratio of a long Standard Deviation Over Period to a short Standard Deviation Over Period as as smoothing factor.[1]

## Syntax

${\displaystyle fx=BT\_I\_VIDYA(Input1,ShortPeriod,LongPeriod,Alpha)}$