Laplace function

Laplace distribution

Laplace distribution

Density, distribution function, quantile function and random generation for the Laplace distribution.

dlaplace(x, mu = 0, sigma = 1, log = FALSE) plaplace(q, mu = 0, sigma = 1, lower.tail = TRUE, log.p = FALSE) qlaplace(p, mu = 0, sigma = 1, lower.tail = TRUE, log.p = FALSE) rlaplace(n, mu = 0, sigma = 1)

Arguments

  • x, q: vector of quantiles.

  • mu, sigma: location and scale parameters. Scale must be positive.

  • log, log.p: logical; if TRUE, probabilities p are given as log(p).

  • lower.tail: logical; if TRUE (default), probabilities are P[Xx]P[X \le x]

    otherwise, P[X>x]P[X > x].

  • p: vector of probabilities.

  • n: number of observations. If length(n) > 1, the length is taken to be the number required.

Details

Probability density function

f(x)=12σexp(xμσ)f(x)=1/(2σ)exp((xμ)/σ) f(x) = \frac{1}{2\sigma} \exp\left(-\left|\frac{x-\mu}{\sigma}\right|\right)f(x) = 1/(2*\sigma) * exp(-|(x-\mu)/\sigma|)

Cumulative distribution function

F(x)={12exp(xμσ)x<μ112exp(xμσ)xμF(x)=[ifx<mu:]1/2exp((xμ)/σ)[else:]11/2exp((xμ)/σ) F(x) = \left\{\begin{array}{ll}\frac{1}{2} \exp\left(\frac{x-\mu}{\sigma}\right) & x < \mu \\1 - \frac{1}{2} \exp\left(\frac{x-\mu}{\sigma}\right) & x \geq \mu\end{array}\right.F(x) = [if x < mu:] 1/2 * exp((x-\mu)/\sigma)[else:] 1 - 1/2 * exp((x-\mu)/\sigma)

Quantile function

F1(p)={μ+σlog(2p)p<0.5μσlog(2(1p))p0.5F1(p)=[ifp<0.5:]μ+σlog(2p)[else:]μσlog(2(1p)) F^{-1}(p) = \left\{\begin{array}{ll}\mu + \sigma \log(2p) & p < 0.5 \\\mu - \sigma \log(2(1-p)) & p \geq 0.5\end{array}\right.F^-1(p) = [if p < 0.5:] \mu + \sigma * log(2*p)[else:] \mu - \sigma * log(2*(1-p))

Examples

x <- rlaplace(1e5, 5, 16) hist(x, 100, freq = FALSE) curve(dlaplace(x, 5, 16), -200, 200, n = 500, col = "red", add = TRUE) hist(plaplace(x, 5, 16)) plot(ecdf(x)) curve(plaplace(x, 5, 16), -200, 200, n = 500, col = "red", lwd = 2, add = TRUE)

References

Krishnamoorthy, K. (2006). Handbook of Statistical Distributions with Applications. Chapman & Hall/CRC

Forbes, C., Evans, M. Hastings, N., & Peacock, B. (2011). Statistical Distributions. John Wiley & Sons.

  • Maintainer: Tymoteusz Wolodzko
  • License: GPL-2
  • Last published: 2023-11-30