Skip to main content

Fisher Transform (FISHER)

Summary

Ehlers' Fisher Transform: an oscillator that reshapes the midpoint's position in its rolling channel into a near-normal distribution. Extreme values become rare and turning points sharp, where a plain channel position spends much of its time pinned near the edges.

The output is unbounded and centred on zero. A peak or trough marks a likely turn, and the Fisher line crossing its Trigger, the same line one bar later, is the author's entry signal.

Formula

With P = (high + low) / 2 and MaxP, MinP its highest and lowest value over the last optInTimePeriod bars:

r       = ( P - MinP ) / ( MaxP - MinP ), or 0.5 when MaxP = MinP
v       = 0.66 * ( r - 0.5 ) + 0.67 * v[prev]
v       = 0.999 if v > 0.99, -0.999 if v < -0.99
Fisher  = 0.5 * ln( ( 1 + v ) / ( 1 - v ) ) + 0.5 * Fisher[prev]
Trigger = Fisher[prev]

v and Fisher start from 0, so the first Trigger is 0, and the limited v is the one the next bar reads.

Notes

  • A window whose midpoints are all equal takes the neutral position, so a market that does not move decays toward 0. The original divides by the zero range there.

Inputs

  • inHigh — High price of each bar
  • inLow — Low price of each bar

Outputs

  • outFisher — Fisher Transform value
  • outTrigger — Fisher value of the previous bar

Parameters

ParameterTypeDefaultAccepted valuesDescription
optInTimePeriodinteger102–100000Number of bars in the channel the midpoint is located in

Properties

Numerical Stability: Initial Unstable Period

☐ Overlap Input
✅ Independent Y-Axis i
☐ Candlestick
☐ Can Output NaN or ±Inf
☐ Identity at Period 1
☐ Display Shift

Implementation

TA-Lib Definition: fisher.c · fisher.yaml

NativeFile
Cta_FISHER.c
Rustfisher.rs
JavaCore_FISHER.java
C#Core_FISHER.cs

TA-Lib is also available for Python, R and more using a wrapper.

Aliases

Fisher Transform, Ehlers Fisher Transform

See Also

STOCHF · WILLR · MIDPRICE · IBS

References

  • John F. Ehlers, "Using The Fisher Transform", Technical Analysis of Stocks & Commodities, V.20:11 (November 2002), 40-42
  • John F. Ehlers, Cybernetic Analysis for Stocks and Futures, Wiley, 2004
Last Updated: