# invPoisson {#invpoisson}

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

## Syntax {#syntax}

`invPoisson(mean, X)`

## Arguments {#arguments}

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

**X** is a floating scalar or vector between 0 and 1.

## Details {#details}

Return the value of a Poisson inverse cumulative distribution function.

## Examples {#examples}

```
invPoisson(1, [0.91, 0.92, 0.93]);
// output: [2, 3, 3]

invPoisson(3, [0.81, 0.83, 0.95, 0.97, 0.99]);
// output: [4, 5, 6, 7, 8]
```

