Exponential distribution parameter

[nathoze]

In the definition of the exponential distribution with the scale parameter beta, the probability density function should be
\begin{equation*}
\text{Exponential}(y|\beta) = \frac{1}{\beta} , \exp ( -\frac{y}{\beta} ) . \end{equation*}

https://mc-stan.org/docs/functions-reference/positive_continuous_distributions.html#exponential-distribution

Current Version:

v2.18.0

[bob-carpenter]

Like on the Wikipedia page, Stan's parameterized using the inverse scale parameter. See the same link.

Is \beta typically used for scale and \lambda for inverse scale? If so, we should change the name of the parameter to avoid confusion.

[nathoze]

My bad, I thought that the parameterization was with the scale, and not the inverse scale, and that there was a mistake in the pdf definition. Yes, the parameter should be \lambda everywhere. Maybe it's worth writing that it is also the rate parameter to avoid confusion.