Lognormal {base} | R Documentation

## The Log Normal Distribution

### Description

Density, distribution function, quantile function and random generation for the log normal distribution whose logarithm has mean equal to `meanlog` and standard deviation equal to `sdlog`.

### Usage

    dlnorm(x, meanlog = 0, sdlog = 1, log = FALSE)
    plnorm(q, meanlog = 0, sdlog = 1, lower.tail = TRUE, log.p = FALSE)
    qlnorm(p, meanlog = 0, sdlog = 1, lower.tail = TRUE, log.p = FALSE)
    rlnorm(n, meanlog = 0, sdlog = 1)

### Arguments

`x, q` | vector of quantiles.
`p` | vector of probabilities.
`n` | number of observations to generate.
`meanlog, sdlog` | mean and standard deviation of the distribution on the log scale.
`log, log.p` | logical; if TRUE, probabilities p are given as log(p).
`lower.tail` | logical; if TRUE (default), probabilities are P[X <= x], otherwise, P[X > x].

### Details

If `meanlog` or `sdlog` are not specified they assume the default values of `0` and `1` respectively.

The log normal distribution has density

f(x) = 1/(sqrt(2 pi) sigma x) e^-((log x - mu)^2 / (2 sigma^2))

where μ and σ are the mean and standard deviation of the logarithm.

### Value

`dlnorm` gives the density, `plnorm` gives the distribution function, `qlnorm` gives the quantile function, and `rlnorm` generates random deviates.

### Note

The cumulative hazard H(t) = - log(1 - F(t)) is `-plnorm(t, r, lower = FALSE, log = TRUE)`.

### See Also

`dnorm` for the normal distribution.

### Examples

    dlnorm(1) == dnorm(0)
    x <- rlnorm(1000)       # not yet always :
    all(abs(x  -  qlnorm(plnorm(x))) < 1e4 * .Machine$double.eps * x)

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