wickra/docs/wiki/indicators/trend/Indicator-Trima.md

TRIMA

Triangular Moving Average — a simple moving average applied twice, which triangular-weights the window so the middle bars carry the most weight.

Quick reference

Field	Value
Family	Trend
Sub-category	Simple averages
Input type	f64 (single close)
Output type	f64
Output range	unbounded; tracks the input price scale
Default parameters	period is required (no default in either binding)
Warmup period	period
Interpretation	Very smooth price level; the triangular weighting suppresses edge bars.

Formula

TRIMA(n) is SMA stacked on SMA. For period n the two lengths are:

odd  n:  n1 = n2 = (n + 1) / 2
even n:  n1 = n / 2,  n2 = n / 2 + 1
TRIMA_t = SMA_{n2}( SMA_{n1}(price) )_t

Composing two equal-weight means convolves two rectangular windows, which yields a triangular weight profile over the original n closes — the centre bar gets the largest weight, the two edges the smallest. Both stacked SMAs are O(1), so update is O(1) regardless of period.

Parameters

Name	Type	Default	Valid range	Description
period	usize	none	>= 1	Window length. period = 0 errors with Error::PeriodZero. period = 1 and period = 2 degenerate to short SMAs.

There is no Python #[pyo3(signature = …)] default for TRIMA, so wickra.TRIMA(period) requires the period explicitly.

Inputs / Outputs

From crates/wickra-core/src/indicators/trima.rs:

impl Indicator for Trima {
    type Input = f64;
    type Output = f64;
    // update(&mut self, input: f64) -> Option<f64>
}

A single f64 close in, an Option<f64> out. Python maps this to float | None / numpy.ndarray (NaN warmup); Node to number | null / Array<number> (NaN warmup).

Warmup

Trima::new(period).warmup_period() == period. The inner SMA emits after n1 inputs; the outer SMA then needs n2 − 1 more, and n1 + n2 − 1 = n for both the odd and even splits. So the first non-None output lands on exactly the period-th update().

Edge cases

• Constant series. [42.0; n] returns Some(42.0) from input period onward — both SMAs are exact for constants (constant_series_yields_the_constant pins this).
• NaN / infinity inputs. update returns self.outer.value() for a non-finite input without feeding either SMA, so the inner SMA's stale value is never double-counted into the outer SMA. State is left untouched.
• Reset. trima.reset() resets both inner and outer SMAs, restarting the warmup countdown.

Examples

Rust

use wickra::{BatchExt, Indicator, Trima};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut trima = Trima::new(5)?;
    let out: Vec<Option<f64>> = trima.batch(&[1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0]);
    println!("{:?}", out);
    println!("warmup_period = {}", trima.warmup_period());
    Ok(())
}

Output:

[None, None, None, None, Some(3.0), Some(4.0), Some(5.0)]
warmup_period = 5

TRIMA(5) is SMA(3) of SMA(3). SMA(3) of 1..=7 is [_, _, 2, 3, 4, 5, 6]; SMA(3) of that is [_, _, _, _, 3, 4, 5]. This matches the odd_period_reference_values test in crates/wickra-core/src/indicators/trima.rs.

Python

import numpy as np
import wickra as ta

trima = ta.TRIMA(5)
print(trima.batch(np.array([1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0])))
print("warmup_period =", trima.warmup_period())

Output:

[nan nan nan nan  3.  4.  5.]
warmup_period = 5

Node

const ta = require('wickra');
const trima = new ta.TRIMA(5);
console.log(trima.batch([1, 2, 3, 4, 5, 6, 7]));
console.log('warmupPeriod:', trima.warmupPeriod());

Output:

[ NaN, NaN, NaN, NaN, 3, 4, 5 ]
warmupPeriod: 5

Interpretation

Trima is one of the smoothest single-line averages in the library: the triangular weight profile damps the most recent bar far more than a plain Sma does, so whipsaws are rare. The cost is lag — a Trima(n) lags roughly like an Sma(n/2) doubled. Use it as a slow trend filter where a clean, low-noise line matters more than fast reaction; prefer Ema or Hma when responsiveness matters.

Common pitfalls

• Expecting Sma-like lag. Stacking two means roughly doubles the effective lag; size the period accordingly.
• Treating period = 0 as "use a default". Trima::new(0) returns Err(Error::PeriodZero) in Rust and a ValueError in Python.

References

The triangular moving average is a standard double-smoothed SMA; the odd/even split used here (n1, n2) matches TA-Lib's TRIMA.

See also

• Indicator-Sma.md — the building block applied twice.
• Indicator-Wma.md — linear (not triangular) weights.
• Indicator-Smma.md — the other F1 average.
• Indicators-Overview.md — the full taxonomy.