# 3.5.3.2.10 Lognpdf

## Definition

lognpdf(X,mu,sigma) returns values at X of the lognormal probability density function with distribution parameters mu and sigma.

$f(x|\mu ,\sigma )=\frac 1{x\sigma \sqrt{2\pi }}e^{\frac{-(\ln x-\mu )^2}{2\sigma ^2}}$

## Parameters

x (input, double)
$x > 0$
mu (input, double)
mean of the associated normal distribution .
sigma(input, double)
standard deviation of the associated normal distribution.$sigma > 0$