Skip to main content
Track Relative Strength Index
3 / 26
Search the archiveLibrary
Library

1991issue C111-2

Seeded averages and the recursive-update

The relative-strength-index is built from an up-average and a down-average. Those averages begin in a 14-day seed-window and are then refreshed by a recursive-update that uses the prior average, a factor of 13, and today’s matching change or zero.

  • The seed-window forms the first up-average and down-average from the same 14 days of closing changes, each summed and divided by 14.
  • Both averages are stored as absolute, non-negative magnitudes, and relative-strength is the up-average divided by the down-average.
  • The oscillator value is 100 minus 100 divided by one plus relative-strength.
  • After the seed, the recursive-update scales each prior average by 13, adds today’s matching change or zero, and divides by 14, with only one side incremented on a given close.
Entries in this reading1 entry
Current trackRelative Strength Index261 readings

A two-stage construction

The relative-strength-index is a 100-scale oscillator produced from the ratio of an up-average to a down-average after that ratio is shifted by one and inverted.

Editorial reading: treat the relative-strength-index as a two-stage construction problem. A fixed 14-day seed-window creates the first up-average and down-average. A later recursive-update then carries those averages forward so later readings inherit the seed instead of restarting a fresh lookback.

How the seed-window forms the first averages

The seed-window is the opening 14-day block used only to form the first pair of averages.

The first up-average is the sum of positive closing changes over 14 days, divided by 14. The first down-average is the sum of negative closing changes over the same 14 days, divided by 14.

Both averaged inputs are stored as absolute, non-negative magnitudes.

Relative-strength and the oscillator value

Relative-strength is the current up-average divided by the current down-average.

The oscillator value is 100 minus 100 divided by one plus relative-strength.

How the recursive-update carries the seed forward

After the 14-day seed, the recursive-update is the later-day rule that scales each prior average by 13, adds today’s matching change or zero, and divides by 14.

A positive close increments only the up-average. A negative close increments only the down-average, using the absolute size of that down close.

Once the two averages are refreshed, the remaining relative-strength transform is the same as in the seed stage.

Educational research material, not investment advice. Historical source context does not establish present-day performance.
3 of 26 in the Relative Strength Index track
19931-6 pp.Next on Relative Strength IndexRestating relative-strength-index parameters after a smoothing changeA rate-of-change-sum can be formed by adding a 14-period price rate of change to an 11-period price rate of change before any smoothing is applied.
All readings on this track · 26 readings
  1. 1991Constructing the relative strength index from seed and recursive averages
  2. 1991Inverting relative-strength-index closes for same-session rules
  3. 1991Seeded averages and the recursive-update
  4. 1993Restating relative-strength-index parameters after a smoothing change
  5. 1993Relative momentum construction by stretching the relative strength lookback
  6. 1994Constructing relative strength index lookbacks, bands, and confirmation filters
  7. 1994Building the relative-strength-index from signed close changes
  8. 1997Constructing the relative strength index as a bounded up-down close oscillator
  9. 2002Four-line oscillator construction for rule-based entries
  10. 2004Assembling a bounded RSI path
  11. 2004Constructing RSI on highs, lows, and reverse targets
  12. 2004Reverse-engineered RSI as an explicit next-bar price target
  13. 2006Self-adjusting RSI thresholds from the oscillator's own spread
  14. 2006Constructing adaptive overbought and oversold levels for a relative strength index
  15. 2006Relative Strength Index 50-line entry beyond the 70 and 30 extremes
  16. 2007Lock a followable rule set before testing RSI exits
  17. 2008RSI bands as a one-day shift of reverse-engineered levels
  18. 2008Constructing an asymmetrical RSI from adaptive up and down averages
  19. 2010Building a bounded oscillator from a rainbow smoother, relative strength, and inverse Fisher
  20. 2011Two-horizon weekly RSI with moving averages and stops
  21. 2011Percent-offset simple moving average bands with relative-strength confirmation
  22. 2011Fast and slow relative strength index as one mechanical rule book
  23. 2011Price-zone oscillator construction from signed closes
  24. 2015Constructing a zero-lag oscillator against a relative strength index baseline
  25. 2015Relative Strength Index as a baseline in 2015 software listings
  26. 2018Building a Fisherized deviation-scaled oscillator
By fieldIndicators and filters874 readingsBy year1991166 readings
All 261 readings tagged Relative Strength Index
Also on Relative Strength Index5 readings
1985Session windows, volume weights, and divergence in RSI construction1986Constructing bounded relative-strength overlays from oscillator limits1987Constructing the commodity channel, average directional, and relative strength indexes on a shared cycle scale1987Constructing scaled OHLC matrices for study overlays1987Evaluating silver moving averages and RSI by scoring rule