Struct LogNormal 

pub struct LogNormal { /* private fields */ }

A continuous distribution where the logarithm follows a normal distribution.

Useful for modeling positive-valued quantities that are naturally multiplicative or skewed.

Mathematical Properties:

• Support: (0, +∞)
• PDF: f(x) = (1/(xσ√(2π))) × exp(-0.5 × ((ln(x)-μ)/σ)²)
• Mean: exp(μ + σ²/2)
• Variance: (exp(σ²) - 1) × exp(2μ + σ²)
• Relationship: If X ~ LogNormal(μ, σ), then ln(X) ~ Normal(μ, σ)

Example:

// Standard log-normal (median = 1)
let standard = sample(addr!("x"), LogNormal::new(0.0, 1.0).unwrap());

// Positive scale parameter
let scale = sample(addr!("scale"), LogNormal::new(0.0, 0.5).unwrap());

// Income distribution
let income = sample(addr!("income"), LogNormal::new(10.0, 0.8).unwrap())
    .map(|x| x.round() as u64); // Convert to dollars

// Multiplicative error model
let true_value = 100.0;
let measured = sample(addr!("error"), LogNormal::new(0.0, 0.1).unwrap())
    .map(move |error| true_value * error);

Implementations

impl LogNormal

pub fn new(mu: f64, sigma: f64) -> FugueResult<Self>

Create a new LogNormal distribution with validated parameters.

pub fn mu(&self) -> f64

Get the mean of the underlying normal distribution.

pub fn sigma(&self) -> f64

Get the standard deviation of the underlying normal distribution.

Trait Implementations

impl Clone for LogNormal

fn clone(&self) -> LogNormal

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for LogNormal

impl Debug for LogNormal

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

Formats the value using the given formatter.

impl Distribution<f64> for LogNormal

fn sample(&self, rng: &mut dyn RngCore) -> f64

Generate a random sample (with its natural type), T, from the distribution, using the provided random number generator, rng.

fn log_prob(&self, x: &f64) -> LogF64

Compute the log-probability density (continuous) or mass (discrete) of a value, x, from the distribution.

fn clone_box(&self) -> Box<dyn Distribution<f64>>

Clone the distribution into a boxed trait object, Box<dyn Distribution<T>>.

impl Validate for LogNormal

fn validate(&self) -> FugueResult<()>