Evaluates the exponential cumulative probability distribution
function.
Namespace: Imsl.StatAssembly: ImslCS (in ImslCS.dll) Version: 6.5.2.0
Syntax public static double Exponential(
double x,
double scale
)
Public Shared Function Exponential (
x As Double,
scale As Double
) As Double
public:
static double Exponential(
double x,
double scale
)
static member Exponential :
x : float *
scale : float -> float
Parameters
- x
- Type: SystemDouble
A double scalar value representing the argument at which the
function is to be evaluated.
- scale
- Type: SystemDouble
A double scalar value representing the scale parameter,
.
Return Value
Type:
Double
A
double scalar value representing the probability that an
exponential random variable takes on a value less than or equal to
x.
Remarks Method Cdf.Exponential is a special case of the gamma
distribution function, which evaluates the distribution function,
F, with scale parameter b and shape parameter
a, used in the gamma distribution function equal to 1.0.
That is,
where is the gamma
function. (The gamma function is the integral from 0 to of the same integrand as above). The value of the
distribution function at the point x is the
probability that the random variable takes a value less than or
equal to x.
If x is less than or equal to 1.0,
Cdf.Gamma uses a series expansion. Otherwise, a continued
fraction expansion is used. (See Abramowitz and Stegun, 1964.)
See Also