# Poisson Command

From GeoGebra Manual

- Poisson( <Mean> )
- Returns a bar graph of a Poisson distribution with given mean
*λ*. - Poisson( <Mean>, <Boolean Cumulative> )
- Returns a bar graph of a Poisson distribution when
*Cumulative = false*. - Returns a graph of a cumulative Poisson distribution when
*Cumulative = true*. - The first parameter is same as above.
- Poisson( <Mean>, <Variable Value v>, <Boolean Cumulative> )
- Let X be a Poisson random variable.
- Returns P( X =
*v*) when*Cumulative*= false. - Returns P( X ≤
*v*) when*Cumulative*= true. - First parameter is same as above.

**Examples:**`Poisson(3, 1, true)`

yields*0.2*in the*Algebra View*and*\frac{4}{e³} in the*CAS View*.*`Poisson(3, 1, false)`

yields*0.15*in the*Algebra View*and*\frac{3}{e³}*in the*CAS View*.

**Note:**A simplified syntax is available to calculate P(*u*≤ X ≤*v*): e.g.`Poisson(1, 1..5)`

yields*0.63153*, that is the same as Poisson(1, {1, 2, 3, 4, 5}).