Systemic Docs

Name	Type	Description
Slow Window	integer	- Description; The period over which the long-term double exponential moving average (DEMA) is calculated.
Fast Window	integer	- Description; The period over which the short-term double exponential moving average (DEMA) is calculated.
Price	floatarray	- Description; The closing price of the asset for each trading period.

Name	Type	Description
TSI	floatarray	- The TSI is an oscillating indicator that ranges around a zero line, with values typically oscillating above and below zero.

The True Strength Index is a momentum oscillator that shows both the direction and strength of a trend. It applies double smoothing to price changes to filter noise while remaining responsive.

TSI = 100 \times \frac{EMA_{s}(EMA_{l}(\Delta Price))}{EMA_{s}(EMA_{l}(|\Delta Price|))}

Where:

$\Delta Price$ = Current price - Previous price
$EMA_l$ = Long EMA (typically 25)
$EMA_s$ = Short EMA (typically 13)

How It Works

flowchart TD
    subgraph Input["Price Changes"]
        PC["ΔPrice = Close - Previous Close"]
        APC["|ΔPrice| = Absolute value"]
    end
    
    subgraph Smoothing["Double EMA Smoothing"]
        N1["Long EMA of ΔPrice"]
        N2["Short EMA of result"]
        D1["Long EMA of |ΔPrice|"]
        D2["Short EMA of result"]
    end
    
    subgraph Calculation["TSI Calculation"]
        DIV["Numerator ÷ Denominator"]
        MULT["× 100"]
    end
    
    PC --> N1 --> N2 --> DIV
    APC --> D1 --> D2 --> DIV
    DIV --> MULT

Interpreting TSI

TSI Range	Interpretation
+25 to +100	Overbought territory
0 to +25	Moderate bullish momentum
-25 to 0	Moderate bearish momentum
-100 to -25	Oversold territory

flowchart LR
    subgraph Zones["TSI Zones"]
        OB["+25 to +100<br/>Overbought"]
        MB["0 to +25<br/>Bullish"]
        MBR["-25 to 0<br/>Bearish"]
        OS["-100 to -25<br/>Oversold"]
    end
    
    OB --> MB --> MBR --> OS

Trading Strategies

1. Zero Line Crossover

Event	Signal
TSI crosses above 0	Bullish momentum emerging
TSI crosses below 0	Bearish momentum emerging

2. Signal Line Crossover

The signal line (typically 7-period EMA of TSI) provides additional signals:

Event	Signal
TSI crosses above signal	Short-term bullish
TSI crosses below signal	Short-term bearish

3. Divergence Analysis

Pattern	Price	TSI	Implication
Bullish	Lower lows	Higher lows	Potential reversal up
Bearish	Higher highs	Lower highs	Potential reversal down

TSI vs RSI

Aspect	TSI	RSI
Smoothing	Double EMA	Single EMA
Range	-100 to +100	0 to 100
Zero line	✓ Has center line	✗ No true center
Noise	Very smooth	Moderate
Responsiveness	Balanced	More reactive

Common Parameters

Parameter	Default	Description
Long EMA	25	Initial smoothing period
Short EMA	13	Secondary smoothing
Signal Line	7	EMA of TSI for crossovers

Advantages

Dual information — Shows both direction (±) and strength (magnitude)
Smooth output — Double smoothing reduces whipsaws
Clear center line — Zero provides natural trend boundary
Divergence friendly — Excellent for spotting divergences

Disadvantages

Lagging — Double smoothing introduces delay
Complex — More calculations than simple oscillators
Range variations — Unlike RSI, rarely hits extremes
Best in trends — Less effective in ranging markets

Missing Data

Gaps in the price series (closed-market weekends/holidays, missing prints) are None — never a sentinel, never a stale-carried TSI value:

Scenario	Output
Closed-market gap	`None` at that slot; the double-EMA cascade runs over observed bars only, so `close.diff()` bridges Friday→Monday as an adjacent observed change (a real step, not a discarded weekend delta)
Warm-up (fewer than `window_slow` + `window_fast` observed bars seen)	`None` — never the retired partial-window seed
All bars missing	Every slot `None`, no crash
Live tick on a gap slot	`[None]` — correct and non-starving, not the retired stale-carry value

Indicator Assessment

The following chart positions TSI based on its complexity (ease of understanding and implementation) versus reliability (consistency of signals across market conditions). Points closer to the top indicate higher reliability; points to the left indicate lower complexity.

quadrantChart
    title TSI Indicator Assessment
    x-axis Low Complexity --> High Complexity
    y-axis Low Reliability --> High Reliability
    quadrant-1 Complex & Reliable
    quadrant-2 Simple & Reliable
    quadrant-3 Simple & Unreliable
    quadrant-4 Complex & Unreliable
    Stocks: [0.55, 0.70]
    Crypto: [0.55, 0.60]

Assessment Breakdown

Dimension	Stocks	Crypto	Notes
Popularity	6/10	5/10	Well-regarded among momentum traders; less mainstream than RSI or MACD
Reliability	7/10	6/10	Double smoothing provides cleaner signals; crypto volatility increases false signals
Complexity	5.5/10	5.5/10	Dual EMA concept is moderately complex; formula straightforward but multi-step
Versatility	6/10	6/10	Works across timeframes; best suited for trend-following strategies
Recent Interest	5/10	5/10	Steady adoption; growing interest as traders seek smoother alternatives to RSI

True Strength Index

Inputs

Outputs