[Rd] RFC: d/p/q/rgamma
Thu, 6 Sep 2001 10:15:43 +0200
>>>>> Prof Brian Ripley writes:
> dgamma and friends in S are documented as
> dgamma(x, shape, rate=1)
> pgamma(q, shape, rate=1)
> qgamma(p, shape, rate=1)
> rgamma(n, shape, rate=1)
> whereas R has
> dgamma(x, shape, scale=1, log = FALSE)
> pgamma(q, shape, scale=1, lower.tail = TRUE, log.p = FALSE)
> qgamma(p, shape, scale=1, lower.tail = TRUE, log.p = FALSE)
> rgamma(n, shape, scale=1)
> Note the use of rate vs scale. Indeed, as both S and R use `rate' for
> exponential this seems somewhat strange, and the only such
> inconsistency I can find.
> I propose that we add a `rate' argument to d/p/q/rgamma as an
> alternative to `scale', which is easily done. The question is where?
> I think we have a trap here for most users, who will happily copy
> dgamma(x, 17, 0.3)
> from their S-PLUS example sheet, and get the wrong answer. My preference
> would be to have
> dgamma(x, shape, rate, scale=1, log = FALSE)
> etc. That would break existing R code using positional matching.
> Question: is there any?
One could find out by unpackaging all CRAN packages and grepping for
usages of *gamma in the code.
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