Struct StdDev 

pub struct StdDev { /* private fields */ }

Rolling population standard deviation over the last period values.

mean     = (1/n) · Σ price
variance = (1/n) · Σ price² − mean²
StdDev   = √variance

This is the population standard deviation (divisor n, not n − 1) — the same dispersion measure that drives BollingerBands. It is maintained as an O(1) rolling state machine: a running sum and a running sum-of-squares, updated by one add and one subtract per bar. Tiny negative variances from floating-point cancellation are clamped to zero before the square root.

Example

use wickra_core::{Indicator, StdDev};

let mut indicator = StdDev::new(20).unwrap();
let mut last = None;
for i in 0..80 {
    last = indicator.update(100.0 + (f64::from(i) * 0.3).sin() * 5.0);
}
assert!(last.is_some());

Implementations

impl StdDev

pub fn new(period: usize) -> Result<Self>

Construct a new rolling standard deviation with the given period.

Errors

Returns Error::PeriodZero if period == 0.

pub const fn period(&self) -> usize

Configured period.

pub const fn value(&self) -> Option<f64>

Current value if available.

Trait Implementations

impl Clone for StdDev

fn clone(&self) -> StdDev

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for StdDev

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Indicator for StdDev

type Input = f64

Type of one input data point (typically f64 for a price, or Candle / Tick).

type Output = f64

Type of one output value.

fn update(&mut self, input: f64) -> Option<f64>

Feed one new data point into the indicator and return the freshly computed output, or None if the indicator is still warming up.

fn reset(&mut self)

Reset all internal state, leaving the indicator equivalent to a freshly constructed instance with the same parameters.

fn warmup_period(&self) -> usize

Number of inputs required before the first non-None output can be produced.

fn is_ready(&self) -> bool

Whether the indicator has emitted at least one value since the last reset.

fn name(&self) -> &'static str

Stable, human-readable indicator name. Used by chaining and diagnostics.