Swing Index

Swing Index computes Wilder's per-bar reading as published, then solves its one modern problem: the scale. The Swing Index folds the close-to-close change, both bars' open-close positions and the dominant excursion from the prior close into one signed number, scaled by the limit move T that his era's futures exchanges provided and most modern markets do not. Auto mode in this first faithful build sets T to the highest excursion over a lookback, so the largest recent swing reads near the extremes; the line colors by sign over a gradient fill, framed by dashed strong-swing levels.

How to Trade the Swing Index?

• Sign: above zero the net two-bar change is bullish, below zero bearish — zero crossings carry alerts both ways.
• Strong swings: readings beyond the Strong Swing Levels mark single bars doing unusual directional work, with crossing alerts on each side.
• Breakout validation: a fresh high over the Breakout Lookback met by a strong positive reading fires Validated New High — Wilder's argument that the extreme is genuine rather than a spike; the mirrored check covers new lows.

Where no limit move exists T is a convention, so the sign and the relative size of readings do the work — the effective T is exposed in the data window.

Swing Index Settings

• Limit Move (T) (default Auto (Highest Excursion)): how the scaling factor is set; Fixed Value uses the entered constant.
• Fixed Limit Move Value (default 1.0): T in price units for Fixed Value mode.
• Auto Scaling Lookback (default 252): bars inspected for the highest excursion in Auto mode.
• Strong Swing Levels (default 50 / -50): thresholds used by the strong-swing and validation alerts; tune them to the instrument.
• Breakout Lookback (default 20): window defining the new highs and lows the validation alerts test.

Frequently Asked Questions

When should I use the Accumulative Swing Index instead?

When you want the line Wilder actually drew on: the Accumulative Swing Index totals these per-bar values into a synthetic price line for trendline and swing work. This build exposes the raw per-bar material.

Why does my reading differ from another implementation's?

Almost always T. Without a real limit move every implementation picks its own scaling convention, and absolute readings only match when both use the same constant. Fixed Value mode lets you reproduce a known one.

Are Auto-scaled readings comparable across symbols?

Comparable in spirit, not in value: each symbol is scaled by its own largest recent excursion. Treat the strong-swing levels as per-instrument conventions.