# poissrnd

Random numbers from Poisson distribution

## Syntax

``r = poissrnd(lambda)``
``r = poissrnd(lambda,sz1,...,szN)``
``r = poissrnd(lambda,sz)``

## Description

example

````r = poissrnd(lambda)` generates random numbers from the Poisson distribution specified by the rate parameter `lambda`.`lambda` can be a scalar, vector, matrix, or multidimensional array.```

example

````r = poissrnd(lambda,sz1,...,szN)` generates an array of random numbers from the Poisson distribution with the scalar rate parameter `lambda`, where `sz1,...,szN` indicates the size of each dimension.```

example

````r = poissrnd(lambda,sz)` generates an array of random numbers from the Poisson distribution with the scalar rate parameter `lambda`, where vector `sz` specifies `size(r)`.```

## Examples

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Generate an array of random numbers from the Poisson distributions. Specify the average rate for each distribution.

`lambda = 10:2:20`
```lambda = 1×6 10 12 14 16 18 20 ```

Generate random numbers from the Poisson distributions.

`r = poissrnd(lambda)`
```r = 1×6 14 13 14 9 14 31 ```

Generate an array of random numbers from one Poisson distribution. Here, the distribution parameter `lambda` is a scalar.

Use the `poissrnd` function to generate random numbers from the Poisson distribution with the average rate 20. The function returns one number.

`r_scalar = poissrnd(20)`
```r_scalar = 9 ```

Generate a 2-by-3 array of random numbers from the same distribution by specifying the required array dimensions.

`r_array = poissrnd(20,2,3)`
```r_array = 2×3 13 14 18 26 16 21 ```

Alternatively, specify the required array dimensions as a vector.

`r_array = poissrnd(20,[2 3])`
```r_array = 2×3 22 27 22 25 19 21 ```

## Input Arguments

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Rate parameters, specified as a positive value or array of positive values. The rate parameter indicates the average number of events in a given time interval.

Example: `2`

Data Types: `single` | `double`

Size of each dimension, specified as separate arguments of integers. For example, specifying `5,3,2` generates a 5-by-3-by-2 array of random numbers from the Poisson probability distribution.

If `lambda` is an array, then the specified dimensions `sz1,...,szN` must match the dimensions of `lambda`.

• If you specify a single value `sz1`, then `r` is a square matrix of size `sz1`-by-`sz1`.

• If the size of any dimension is `0` or negative, then `r` is an empty array.

• Beyond the second dimension, `poissrnd` ignores trailing dimensions with a size of 1. For example, `poissrnd``(5,3,1,1,1)` produces a 3-by-1 vector of random numbers from the Poisson distribution with rate parameter 5.

Example: `5,3,2`

Data Types: `single` | `double`

Size of each dimension, specified as a row vector of integers. For example, specifying `[5 3 2]` generates a 5-by-3-by-2 array of random numbers from the Poisson probability distribution.

If `lambda` is an array, then the specified dimensions `sz` must match the dimensions of `lambda`.

• If you specify a single value `[sz1]`, then `r` is a square matrix of size `sz1`-by-`sz1`.

• If the size of any dimension is `0` or negative, then `r` is an empty array.

• Beyond the second dimension, `poissrnd` ignores trailing dimensions with a size of 1. For example, `poissrnd``(5,[3,1,1,1])` produces a 3-by-1 vector of random numbers from the Poisson distribution with rate parameter 5.

Example: `[5 3 2]`

Data Types: `single` | `double`

## Output Arguments

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Random numbers from the Poisson distribution, returned as a scalar value or an array of scalar values.

Data Types: `single` | `double`

## Alternative Functionality

• `poissrnd` is a function specific to Poisson distribution. Statistics and Machine Learning Toolbox™ also offers the generic function `random`, which supports various probability distributions. To use `random`, specify the probability distribution name and its parameters. Alternatively, create a `PoissonDistribution` probability distribution object and pass the object as an input argument. Note that the distribution-specific function `poissrnd` is faster than the generic function `random`.

• To generate random numbers interactively, use `randtool`, a user interface for random number generation.

## Version History

Introduced before R2006a