# Documentation

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# poissfit

Poisson parameter estimates

## Syntax

`lambdahat = poissfit(data)[lambdahat,lambdaci] = poissfit(data)[lambdahat,lambdaci] = poissfit(data,alpha)`

## Description

`lambdahat = poissfit(data)` returns the maximum likelihood estimate (MLE) of the parameter of the Poisson distribution, λ, given the data `data`.

`[lambdahat,lambdaci] = poissfit(data)` also gives 95% confidence intervals in `lamdaci`.

`[lambdahat,lambdaci] = poissfit(data,alpha)` gives `100(1 - alpha)`% confidence intervals. For example `alpha` = `0.001` yields 99.9% confidence intervals.

The sample mean is the MLE of λ.

`$\stackrel{^}{\lambda }=\frac{1}{n}\sum _{i=1}^{n}{x}_{i}$`

## Examples

```r = poissrnd(5,10,2); [l,lci] = poissfit(r) l = 7.4000 6.3000 lci = 5.8000 4.8000 9.1000 7.9000```

## See Also

#### Introduced before R2006a

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