What are you trying to do?

The current implementation of the StudentsT distribution doesn't allow you to specify a non-centrality parameter ($\delta$). This would be useful because the noncentral-t distribution is useful for power analyses and in Bayesian inference (my personal usecase)

Are you able to help contribute the feature?

See #1819: I'm currently using translations I've made of R's nmath C library, and these translations could be used as the basis for this.