[R] Gelman 2006 half-Cauchy distribution
Berwin A Turlach
berwin at maths.uwa.edu.au
Fri May 28 16:09:42 CEST 2010
G'day Chris,
On Fri, 28 May 2010 08:29:30 -0500
Christopher David Desjardins <cddesjardins at gmail.com> wrote:
> Hi,
> I am trying to recreate the right graph on page 524 of Gelman's 2006
> paper "Prior distributions for variance parameters in hierarchical
> models" in Bayesian Analysis, 3, 515-533. I am only interested,
> however, in recreating the portion of the graph for the overlain
> prior density for the half-Cauchy with scale 25 and not the posterior
> distribution. However, when I try:
>
> curve(dcauchy, from=0, to=200, location=0, scale=25)
Which version of R do you use? This command creates 12 warnings under
R 2.11.0 on my linux machine.
Reading up on the help page of curve() would make you realise that you
cannot pass the location and scale parameter to dcauchy in the manner
you try. I guess you want:
R> prior <- function(x) 2*dcauchy(x,location=0, scale=25)
R> curve(prior, from=0, to=200)
or, more compactly,
R> curve(2*dcauchy(x, location=0, scale=25), from=0, to=200)
Cheers,
Berwin
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