# cdfPoisson {#cdfpoisson}

**Parent topic:**[Functions](../../Functions/category.md)

## Syntax {#syntax}

`cdfPoisson(mean, X)`

## Arguments {#arguments}

**mean** is the mean of a Poisson distribution.

**X** is a numeric scalar or vector.

## Details {#details}

Return the value of the cumulative distribution function of a Poisson distribution.

## Examples {#examples}

```
cdfPoisson(1, [-1, 0, 1, 2, 3]);
// output: [0, 0.367879, 0.735759, 0.919699, 0.981012]

cdfPoisson(1, [1, 3, 5, 7, 9]);
// output: [0.735759, 0.981012, 0.999406, 0.99999, 1]
```

