Extreme gap

How wide the last 100 closes spread, as a share of their lowest close.

ExtremeGap takes the highest and lowest close over the last 100 bars and divides their difference by the lowest close. The result is a ratio, so 0.002 means the 100-bar range spans 0.2% of that low. It uses closing prices only and carries no direction, so it measures how wide the range is, not which way price is leaning.

How to read it

The line sits in its own pane below the price and is never negative.
Values are ratios: 0.002 means the last 100 closes spanned 0.2% of their low. On a sample month of SPY one-minute bars the median was about 0.002.
Low readings, below about 0.0007, mean the last 100 closes stayed in a tight band. High readings, above about 0.006, mean price has covered a wide range recently.
The line steps when a new high or low enters the 100-bar window and drops when an old extreme leaves it 100 bars later.

What it outputs

Range as share of low: The highest close minus the lowest close over the last 100 bars, divided by the lowest close. The result is never negative.

Pitfalls

The name and docstring suggest trend strength, but this is only range width. A steady climb and a choppy sideways market can both give a high reading, so pair it with a direction indicator.
It uses closing prices only, so an intrabar spike to a new high or low leaves no trace. Support and resistance here are just the 100-bar close extremes, not levels price has respected.
The first 99 bars of loaded history show no value. Dividing by the lowest close means the same dollar range reads higher at a lower price, so compare values within one symbol.