# Elder-ray Index

Created by Alexander Elder, the Elder-ray Index, also known as Bull and Bear Power, is an oscillator that depicts buying and selling pressure. It compares current high/low prices against an Exponential Moving Average. [Discuss] ðŸ’¬

```
// C# usage syntax
IEnumerable<ElderRayResult> results =
quotes.GetElderRay(lookbackPeriods);
```

## Parameters

`lookbackPeriods`

* int* - Number of periods (

`N`

) for the underlying EMA evaluation. Must be greater than 0. Default is 13.### Historical quotes requirements

You must have at least `2Ã—N`

or `N+100`

periods of `quotes`

, whichever is more, to cover the warmup and convergence periods. Since this uses a smoothing technique, we recommend you use at least `N+250`

data points prior to the intended usage date for better precision.

`quotes`

is a collection of generic `TQuote`

historical price quotes. It should have a consistent frequency (day, hour, minute, etc). See the Guide for more information.

## Response

```
IEnumerable<ElderRayResult>
```

- This method returns a time series of all available indicator values for the
`quotes`

provided. - It always returns the same number of elements as there are in the historical quotes.
- It does not return a single incremental indicator value.
- The first
`N-1`

periods will have`null`

indicator values since thereâ€™s not enough data to calculate.

âšž

Convergence warning: The first`N+100`

periods will have decreasing magnitude, convergence-related precision errors that can be as high as ~5% deviation in indicator values for earlier periods.

### ElderRayResult

`Date`

* DateTime* - Date from evaluated

`TQuote`

`Ema`

* double* - Exponential moving average

`BullPower`

* double* - Bull Power

`BearPower`

* double* - Bear Power

### Utilities

See Utilities and helpers for more information.

## Chaining

Results can be further processed on `(BullPower+BearPower)`

with additional chain-enabled indicators.

```
// example
var results = quotes
.GetElderRay(..)
.GetEma(..);
```

This indicator must be generated from `quotes`

and **cannot** be generated from results of another chain-enabled indicator or method.