Distribution and quantile precision (was [R] Underflow warnings?)

Thomas Lumley thomas at biostat.washington.edu
Mon Feb 14 17:33:04 CET 2000

On Mon, 14 Feb 2000, John Logsdon wrote:
> On Sun, 13 Feb 2000, Thomas Lumley wrote:
> > 
> > A bigger issue, which we _have_ been working on, is getting closer to full 
> > precision for the probability and quantile functions. 
> >  
> Ah - will this include functions for the logs of densities and quantiles?

Yes: eg from the pre1.0.0 help page for pchisq()


     dchisq(x, df, ncp=0, log = FALSE)
     pchisq(q, df, ncp=0, lower.tail = TRUE, log.p = FALSE)
     qchisq(p, df, ncp=0, lower.tail = TRUE, log.p = FALSE)
     rchisq(n, df)

so we at least have syntax for log densities and log probabilities and
for lower as well as upper tail probabilities. I don't know if all the
underlying functions have been updated or only some of them.


Thomas Lumley
Assistant Professor, Biostatistics
University of Washington, Seattle

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