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I'd love to have these functions available. If I understand correctly, it is possible to work around it by using gburtini\Distributions\Accessories\BetaFunction. I'm doing this to get a graph of the distribution curve to display it visually:

    $last = 0; $data = array();
    for ($i=0;$i<=1.0;$i+=0.01) {
        $b = BetaFunction::incompleteBetaFunction($i, $this->alpha, $this->beta);
        $data[] = $b-$last;
        $last = $b;
    }

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For beta

https://en.wikipedia.org/wiki/Beta_distribution

CDF is definded by integral

https://en.wikipedia.org/wiki/Beta_function#Incomplete_beta_function

Because of different needs we should balance between time and accuracy. I propose the following interface

$beta->cdf($x, ?$params) // optional $params as associative array with info about precision

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@tvogt it looks good. I will test behavior of your solution tomorrow and type there about potential boundaries. I didn't know that this package has incompleteBetaFunction implemented.

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Look into Accessories\BetaFunction - there is quite a bit of code there which I mostly don't understand (I mean I understand the code, but not what it means).

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@tvogt I added the following CDF for Beta Distribution.

    /**
     * @param $x
     * @return float|int
     * Definition: https://en.wikipedia.org/wiki/Beta_function#Incomplete_beta_function
     * we can calculate integral but better idea is to use fraction representation:
     * In our code there is implemented method http://functions.wolfram.com/GammaBetaErf/Beta3/10/
     */
    public function cdf($x)
    {
        return BetaFunction::incompleteBetaFunction($x, $this->alpha, $this->beta);
    }

In link

http://functions.wolfram.com/GammaBetaErf/Beta3/10/

You have a representation of this function that has quite nice convergence. Integrating is more intuitive, but due to numerical reason is not preferred.

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