

   TThhee EExxppoonneennttiiaall DDiissttrriibbuuttiioonn

        dexp(x, rate = 1)
        pexp(q, rate = 1)
        qexp(p, rate = 1)
        rexp(n, rate = 1)

   AArrgguummeennttss::

        x q: vector of quantiles.

          p: vector of probabilities.

          n: number of observations to generate.

       rate: vector of rates.

   VVaalluuee::

        These functions provide information about the exponen-
        tial distribution with rate `rate' (i.e., mean
        `1/rate').  `dexp' gives the density, `pexp' gives the
        distribution function, `qexp' gives the quantile func-
        tion and `rexp' generates random deviates.

        If `rate' is not specified, it assumes the default
        value of `1'.

        The exponential distribution with rate lambda has den-
        sity

                     f(x) = lambda e^(- lambda x)

        for x >= 0.

   SSeeee AAllssoo::

        `exp' for the exponential function, `dgamma' for the
        gamma distribution and `dweibull' for the Weibull dis-
        tribution, both of which generalize the exponential.

   EExxaammpplleess::

        dexp(1) - exp(-1) #-> 0
        r <- rexp(100)
        all(abs(1 - dexp(1, r) / (r*exp(-r))) < 1e-14)

