# Efficiency ratio

`efficiency_ratio`

How directly the price moved: 1 for a straight line, near 0 for noise.

## Inputs

| Name | Type | Default | Range |
| --- | --- | --- | --- |
| source | source | close |  |
| period | int | 10 | 1 to 5000 |

## Outputs

| Name | Kind |
| --- | --- |
| efficiency_ratio | value |

Warm-up: period bars (10 at the defaults).

Repaints: No.

## Formula

ER[i] = |x[i] - x[i-period]| / sum(|x[j] - x[j-1]|) for j from i-period+1 to i

When the sum is zero, ER is 0. A window holding a missing value has no value.