Skew-t Distribution LPDF

[Nelson_Lima_de_Souza_Filh]

Hi, I’m building a model where I need the lcdf of a skew-t. Below is the pdf form of Skew-t,

Azzalini develops this function in R in package sn with the name of pst.
If anyone can help me write this lcdf in stan I would appreciate it a lot.

[spinkney]

Skew T distribution in Stan

I have the generalized_skew_t lpdf and lcdf functions at helpful_stan_functions/skew_generalized_t.stanfunctions at main · spinkney/helpful_stan_functions · GitHub. These reduce to skew T by setting p = 2. However, it appears that the parameterization is different from the sn R package. Due to the use of lambda which is between -1, 1. The Skew T that it reduces to is the skew T from https://www.ssc.wisc.edu/~bhansen/papers/ier_94.pdf equation 10 (p. 710, pdf p. 6). I also have the quantile fun…

[Nelson_Lima_de_Souza_Filh]

Thanks but the parameterization I use has -Inf <lambda <Inf. I forgot to inform you that

If anyone else can help me I’ll appreciate it.