Erlang

Interface

erlang(n:int, r:real) : real

where n>=1 and r>0.0. Returns a drawing from an n-Erlang distribution with intensity r.

A drawing from an n-Erlang distribution can be derived by addition of n drawings from a exponential distribution.

Raises Erlang exception, if n<1 or r<=0.0.

Characteristics

Mean: n/r
Variance: n/r^2

Density functions for n-Erlang distributions:

Density functions for Erlang distributions

Example

erlang(100,50.0)

A shop gives each 100th customer a present. The arrival time between customers is exponentially distributed with intensity r=50.0 per hour. The sums of the arrival times between customers is Erlang distributed with parameters n=100 and r=50.0.

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