From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>

Date: Mon, 14 Apr 2008 14:14:20 +0100 (BST)

Date: Mon, 14 Apr 2008 14:14:20 +0100 (BST)

Bill,

We already have erf() and erfc() as examples, and help.search() will find them. I've added erfinv() and erfcinv() to the examples and concept index.

I don't see a good reason to add them to e.g. the 'stats' namespace: it is not as if we wish to encourage people to use them instead of [pq]norm. I doubt that those for whom help.search("erf") is too difficult will even manage to find the Wiki (when it is operational).

Brian

On Mon, 14 Apr 2008, Bill.Venables_at_csiro.au wrote:

> That's not a bad idea. If the wiki comes up again, please do it.

*>
**> They are so short I wonder that they just can't go in to base R though.
**> It's not particularly matlab terminology, it's engineering and physics
**> terminology pretty widely. See, e.g. Abramowitz and Stegun.
**>
**> For specifcity, here are the four I would suggest.
**>
**> erf <- function (x) 2 * pnorm(x * sqrt(2)) - 1
**> erfc <- function (x) 2 * pnorm(x * sqrt(2), lower = FALSE)
**> erfinv <- function (x) qnorm((1 + x)/2)/sqrt(2)
**> erfcinv <- function (x) qnorm(x/2, lower = FALSE)/sqrt(2)
**>
**> But I don't feel strongly enough about it to push it on R-devel myself
**> right now.
**> I always forget the connexion and it seems to come up when you least
**> expect it. I've just added them to my little horde of useful stuff, so
**> I'm OK now!
**>
**> Bill.
**>
**>
**> Bill Venables
**> CSIRO Laboratories
**> PO Box 120, Cleveland, 4163
**> AUSTRALIA
**> Office Phone (email preferred): +61 7 3826 7251
**> Fax (if absolutely necessary): +61 7 3826 7304
**> Mobile: +61 4 8819 4402
**> Home Phone: +61 7 3286 7700
**> mailto:Bill.Venables_at_csiro.au
**> http://www.cmis.csiro.au/bill.venables/
**>
**> -----Original Message-----
**> From: r-help-bounces_at_r-project.org [mailto:r-help-bounces_at_r-project.org]
**> On Behalf Of Ben Bolker
**> Sent: Monday, 14 April 2008 11:00 AM
**> To: r-help_at_stat.math.ethz.ch
**> Subject: Re: [R] R equivalent of erfcinv in matlab
**>
**> <Bill.Venables <at> csiro.au> writes:
**>
**>>
**>> At a guess ...
**>>
**>>> erfc <- function(x) 2 * pnorm(x * sqrt(2), lower = FALSE)
**>>> erfcinv <- function(x) qnorm(x/2, lower = FALSE)/sqrt(2)
**>>> erfc(0.3)
**>> [1] 0.6713732
**>>> erfcinv(erfc(0.3))
**>> [1] 0.3
**>>>
**>>
**>> It may not hurt to include these wrappers in R for matlab refugees.
**>> They seem to be coming thick and fast these days.
**>>
**>
**> There's a page on the wiki about matlab to R (actually
**> I think it's titled "Octave to R" -- this could go on
**> there whether or not it gets into base R.
**> I would put it on myself, right now, but the wiki
**> appears to be down?
**>
**> ping wiki.r-project.org
**> PING econum.umh.ac.be (193.190.194.5) 56(84) bytes of data.
**>
**> Ben Bolker
*

-- Brian D. Ripley, ripley_at_stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-help_at_r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.Received on Mon 14 Apr 2008 - 13:34:54 GMT

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