Asymmetrical RSI is an indicator that computes a custom relative strength index from the rate of change of a user-selected source. It plots the resulting ARSI line in a separate pane with color coding that turns green above the overbought level and red below t
Indicator · Pine Script v6 · Own pane
FSI - Ehlers Fourier Series Indicator
This Pine Script indicator computes the FSI using Ehlers Fourier series analysis on the close price.
GitHub stars99on the repository
Pine versionv6current
Lines of code51
Settings2inputs
LicenceApache-2.0
Last update4 weeks ago27 Sep 2026
Add It to Your TradingView Chart
- 1Copy the scriptPress Copy script above, or the copy button on the code below.
- 2Open the Pine EditorOpen a TradingView chart and choose Pine Editor at the bottom of the screen.
- 3Paste over the templateCreate a new indicator, select all of the template text and paste. Press Save and give it a name.
- 4Add it to the chartPress Add to chart, then adjust the settings with the gear icon next to its name.
Source Code
51 lines of Pine Script v6 from lib/cycles/fsi/fsi.pine, published under Apache-2.0. Keep the author's credit and licence lines when you reuse it.
// This Pine Script™ code is subject to the terms of the Mozilla Public License 2.0
// https://mozilla.org/MPL/2.0/
// © QuanTAlib
//@version=6
indicator("FSI - Ehlers Fourier Series Indicator", shorttitle="FSI", overlay=false)
// Inputs
x = input.int(20, "Fundamental Cycle Period", minval=6)
bw = input.float(0.1, "Bandwidth", minval=0.001, step=0.01)
// Fundamental bandpass coefficients
L1 = math.cos(2 * math.pi / x)
G1 = math.cos(bw * 2 * math.pi / x)
S1 = 1 / G1 - math.sqrt(1 / (G1 * G1) - 1)
// 2nd harmonic coefficients (period = x/2)
L2 = math.cos(2 * math.pi / (x / 2))
G2 = math.cos(bw * 2 * math.pi / (x / 2))
S2 = 1 / G2 - math.sqrt(1 / (G2 * G2) - 1)
// 3rd harmonic coefficients (period = x/3)
L3 = math.cos(2 * math.pi / (x / 3))
G3 = math.cos(bw * 2 * math.pi / (x / 3))
S3 = 1 / G3 - math.sqrt(1 / (G3 * G3) - 1)
// Bandpass filters
float BP1 = 0.0
BP1 := 0.5 * (1 - S1) * (close - close[2]) + L1 * (1 + S1) * nz(BP1[1]) - S1 * nz(BP1[2])
float BP2 = 0.0
BP2 := 0.5 * (1 - S2) * (close - close[2]) + L2 * (1 + S2) * nz(BP2[1]) - S2 * nz(BP2[2])
float BP3 = 0.0
BP3 := 0.5 * (1 - S3) * (close - close[2]) + L3 * (1 + S3) * nz(BP3[1]) - S3 * nz(BP3[2])
// Quadrature components (differentiation-based 90° phase shift)
Q1 = (x / (2 * math.pi)) * (BP1 - nz(BP1[1]))
Q2 = (x / (2 * math.pi)) * (BP2 - nz(BP2[1]))
Q3 = (x / (2 * math.pi)) * (BP3 - nz(BP3[1]))
// Power estimation (rolling sum over x bars)
P1 = math.sum(BP1 * BP1 + Q1 * Q1, x)
P2 = math.sum(BP2 * BP2 + Q2 * Q2, x)
P3 = math.sum(BP3 * BP3 + Q3 * Q3, x)
// Amplitude-weighted reconstruction
fsi = P1 > 0 ? BP1 + math.sqrt(P2 / P1) * BP2 + math.sqrt(P3 / P1) * BP3 : BP1
plot(fsi, "FSI", color.yellow, 2)
hline(0, "Zero", color.gray, hline.style_dotted)
Overview
FSI - Ehlers Fourier Series Indicator applies fundamental and harmonic bandpass filters, derives quadrature components for phase shift, estimates signal power over the cycle period, and reconstructs the amplitude-weighted output. The indicator plots a single line in a separate pane. The fundamental cycle period and bandwidth settings adjust filter frequencies and response characteristics. It draws on the price chart in a dedicated pane for cycle detection.
- Ehlers Fourier Series
- bandpass filters
- quadrature components
- power estimation
- amplitude reconstruction
Details
Published by
mihakralj on GitHub
Code credit
QuanTAlib, as written in the script's header
Type
Indicator, Pine Script v6
Draws
Separate pane below the chart
Category
Oscillators & momentum
Markets
Any symbol
Timeframes
Any timeframe
Risk Notes
No repainting, lookahead or stacked entries were found in its code or README. That says nothing about how well it works: test it first.
Topics
algorithmic-tradingcsharpdotnetpinescriptpythonquantitative-financesimdta-libtechnical-analysistechnical-indicators
Settings
The inputs you can change from the gear icon on the chart. Defaults are the author's.
| Setting | Type | Default | Variable |
|---|---|---|---|
| Fundamental Cycle Period | int | 20 | x |
| Bandwidth | float | 0.1 | bw |
Third-party code. ForexR did not write, test or endorse this script, and the summary above was generated automatically from its code and README. Indicators describe the past, and a strategy's backtest can look better than live trading, especially when a script repaints. Check it in the Strategy Tester and on a demo account before you rely on it.
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