# DExp-class

From distr v2.6
by Peter Ruckdeschel

##### Class "DExp"

The double exponential or Laplace distribution with rate $\lambda$ has density $$ f(x) = \frac{1}{2}\lambda {e}^{- \lambda |x|}$$

- Keywords
- distribution

##### Objects from the Class

Objects can be created by calls of the form `DExp(rate)`

.
This object is a double exponential (or Laplace) distribution.

##### Slots

`img`

- Object of class
`"Reals"`

: The space of the image of this distribution has got dimension 1 and the name "Real Space". `param`

- Object of class
`"ExpParameter"`

: the parameter of this distribution (rate), declared at its instantiation `r`

- Object of class
`"function"`

: generates random numbers (calls function rexp) `d`

- Object of class
`"function"`

: density function (calls function dexp) `p`

- Object of class
`"function"`

: cumulative function (calls function pexp) `q`

- Object of class
`"function"`

: inverse of the cumulative function (calls function qexp) `.withArith`

- logical: used internally to issue warnings as to interpretation of arithmetics
`.withSim`

- logical: used internally to issue warnings as to accuracy
`.logExact`

- logical: used internally to flag the case where there are explicit formulae for the log version of density, cdf, and quantile function
`.lowerExact`

- logical: used internally to flag the case where there are explicit formulae for the lower tail version of cdf and quantile function
`Symmetry`

- object of class
`"DistributionSymmetry"`

; used internally to avoid unnecessary calculations.

##### Extends

Class `"AbscontDistribution"`

, directly.
Class `"UnivariateDistribution"`

, by class `"AbscontDistribution"`

.
Class `"Distribution"`

, by class `"AbscontDistribution"`

.

##### Methods

- initialize
`signature(.Object = "DExp")`

: initialize method- rate
`signature(object = "DExp")`

: returns the slot rate of the parameter of the distribution- rate<-
`signature(object = "DExp")`

: modifies the slot rate of the parameter of the distribution- *
`signature(e1 = "DExp", e2 = "numeric")`

: For the Laplace distribution we use its closedness under scaling transformations.

##### See Also

`Exp-class`

`ExpParameter-class`

`AbscontDistribution-class`

`Reals-class`

`rexp`

##### Examples

```
D <- DExp(rate = 1) # D is a Laplace distribution with rate = 1.
r(D)(1) # one random number generated from this distribution, e.g. 0.4190765
d(D)(1) # Density of this distribution is 0.1839397 for x = 1.
p(D)(1) # Probability that x < 1 is 0.8160603.
q(D)(.1) # Probability that x < -1.609438 is 0.1.
rate(D) # rate of this distribution is 1.
rate(D) <- 2 # rate of this distribution is now 2.
3*D ### still a DExp -distribution
```

*Documentation reproduced from package distr, version 2.6, License: LGPL-3*

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