[SciPy-user] accuracy of stats.gamma.pdf

[Pauli Virtanen]

Thu, 29 Jan 2009 10:48:01 +0100, Nicolas Chopin wrote:

> Dear list,
> when I compute:
> 
> stats.gamma.pdf(5.,2.,5.)
> 
> I get:
> array([0.])
> 
> whereas the same command in R outputs:
>  > dgamma(5.,2.,5.)
> [1] 1.735993e-09

Reading help(dgamma) in R, and help(scipy.stats.gamma.pdf) reveals the 
following:

In R, the third parameter to dgamma is the rate parameter. In Scipy, the 
third parameter is the location parameter, ie.

    scipy.stats.gamma.pdf(x, a, mu) == dgamma(x - mu, a)

It appears that scipy.stats.gamma doesn't have a scale parameter.

-- 
Pauli Virtanen