Exponential
The Exponential Distribution
Description
    Calculates density, cumulative probability, quantile, and 
    generate random sample for the exponential distribution (continuous).
Usage
dexp(x, rate = 1, log = FALSE) # density
pexp(q, rate = 1, lower.tail = TRUE, log.p = FALSE) # probability
qexp(p, rate = 1, lower.tail = TRUE, log.p = FALSE) # quantile
rexp(n, rate = 1) # random
Arguments
    
| x, q | numeric vectors in the range [0, Inf) that specify the quantiles. | 
    | p | a numeric vector in the range [0, 1] that specifies the probabilities. | 
    | n | an integer scalar in the range [0, Inf) that specifies the number of random samples requested.
        If the input value is not an integer, it is truncated.
        If length(n) is greater than 1,
        the random function returns length(n) random samples. | 
    | rate | a numeric vector in the range [0, Inf) that specifies the rate parameter. | 
    | log | a logical value.
        If FALSE (default), the density function returns the density itself.
        If TRUE, it returns the log of the density. | 
    | lower.tail | a logical value.
        If TRUE (default), the probability supplied to the quantile function 
        or returned by the probability function is P[X <= x]. 
        If FALSE, it is P[X > x]. | 
    | log.p | a logical value.
        If FALSE (default), the probability supplied to the quantile function
        or returned by the probability function is the probability itself.
        If TRUE, it is the log of the probability. | 
 
Details
    The distribution parameter(s) are replicated cyclically to be the same length as 
    the input x, q, p, or the number of random samples requested.
    Missing values (NAs) in the input or the distribution parameter(s) 
    will cause the corresponding elements of the result to be missing.
Value
    returns density (dexp),
    cumulative probability (pexp),
    quantile (qexp), or
    random sample (rexp)
    for the exponential distribution with parameter rate.
Side Effects
    If the .Random.seed dataset exists, the random sample function updates its value.
    The random sample function creates the .Random.seed dataset if it does not exist.
Background
    The exponential distributions is a family of continuous probability distributions
    defined on the interval [0, Inf) and parameterized by a positive parameter rate.
References
    Johnson, N. L. and Kotz, S. (1970).
    Continuous Univariate Distributions, vol. 1 and 2.
    Houghton-Mifflin, Boston.
See Also
Examples
dexp(seq(0.0001, 6, length = 20))