wickra/docs/wiki/indicators/momentum-oscillators/Indicator-Cmo.md

CMO

Chande Momentum Oscillator — a bounded [−100, 100] momentum gauge from the unsmoothed sum of gains versus losses.

Quick reference

Field	Value
Family	Momentum Oscillators
Input type	f64 (single close)
Output type	f64
Output range	[−100, 100]
Default parameters	period = 14 (Python)
Warmup period	period + 1
Interpretation	+100 pure gains, −100 pure losses, 0 balanced.

Formula

Over the last period price changes, sum the gains and the losses separately:

gain_t = max(price_t − price_{t−1}, 0)
loss_t = max(price_{t−1} − price_t, 0)
CMO    = 100 · (Σ gain − Σ loss) / (Σ gain + Σ loss)

Unlike RSI — which Wilder-smooths the gain/loss averages — CMO sums them raw, with equal weight on every change in the window. That makes it faster and wider-swinging than RSI at the same period.

Parameters

Name	Type	Default	Valid range	Description
period	usize	14 (Python)	>= 1	Number of price changes summed. period = 0 errors with Error::PeriodZero.

The Python binding defaults period to 14 via #[pyo3(signature = (period=14))].

Inputs / Outputs

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

impl Indicator for Cmo {
    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

Cmo::new(period).warmup_period() == period + 1. The first price change needs two inputs, and the gain/loss window must hold period changes, so the first non-None output lands on input period + 1.

Edge cases

• Pure trend. A window of only gains returns +100; only losses, −100 (pure_uptrend_saturates_at_plus_100 / pure_downtrend_saturates_at_minus_100 pin this).
• Constant series. A flat series has no gains and no losses; the 0 / 0 is guarded and the output is 0.0 (constant_series_yields_zero pins this).
• NaN / infinity inputs. Non-finite inputs are silently dropped; state is left untouched.
• Reset. cmo.reset() clears the previous price, the gain/loss window and both running sums.

Examples

Rust

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

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut cmo = Cmo::new(3)?;
    let out: Vec<Option<f64>> = cmo.batch(&[10.0, 11.0, 10.0, 12.0]);
    println!("{:?}", out);
    Ok(())
}

Output:

[None, None, None, Some(50.0)]

The three changes are +1, −1, +2: Σ gain = 3, Σ loss = 1, so CMO = 100·(3 − 1)/(3 + 1) = 50. This matches the reference_value test in crates/wickra-core/src/indicators/cmo.rs.

Python

import numpy as np
import wickra as ta

cmo = ta.CMO(3)
print(cmo.batch(np.array([10.0, 11.0, 10.0, 12.0])))

Output:

[nan nan nan 50.]

Node

const ta = require('wickra');
const cmo = new ta.CMO(3);
console.log(cmo.batch([10, 11, 10, 12]));

Output:

[ NaN, NaN, NaN, 50 ]

Interpretation

Cmo is read like other bounded oscillators: readings near +50 and above flag overbought conditions, near −50 and below oversold, and the zero line marks the gain/loss balance point. Because it is unsmoothed it reacts a bar or two sooner than RSI but is noisier — pair it with a slower filter, or use it for divergence rather than raw threshold triggers.

Common pitfalls

• Expecting the [0, 100] RSI scale. Cmo is centred on zero and spans [−100, 100]; an RSI of 30 corresponds to a Cmo near −40.
• Treating it as a smoothed average. Cmo sums raw changes — it is deliberately not Wilder-smoothed.

References

Tushar Chande, The New Technical Trader (1994). The unsmoothed gain/loss sum here matches the original definition and TA-Lib's CMO.

See also

• Indicator-Rsi.md — the Wilder-smoothed relative.
• Indicator-Mom.md — raw price-difference momentum.
• Indicators-Overview.md — the full taxonomy.