[R] sapply() and Monte Carlo

[Czerminski, Ryszard]

Great idea ! I am sure it would be very useful - in particular
to the newcomers to the R-land.

The question is where to put it and how to organize it 
to make it useful ?
Some database approach with web interface would be probably good
in the long run.

R

Ryszard Czerminski   phone: (781)994-0479
ArQule, Inc.         email:ryszard at arqule.com
19 Presidential Way  http://www.arqule.com
Woburn, MA 01801     fax: (781)994-0679


-----Original Message-----
From: Robin Hankin [mailto:r.hankin at auckland.ac.nz]
Sent: Wednesday, June 26, 2002 12:52 AM
To: r-help at stat.math.ethz.ch
Subject: [R] sapply() and Monte Carlo


Dear Helplist

Some time ago, Professor Ripley gave me a tip which I thought was very
very useful for Monte Carlo simulation; I thought I'd pass it on to
the list, and ask whether this or a similar example could be added to
the sapply() manpage.

Suppose I have ten N(0,1) random variables and I'm interested in the
pair that are closest together:

R> min(diff(sort(rnorm(10))))
[1] 0.04438955

To generate a PDF for this statistic one can use sapply() as follows:

R> func <- function(n){min(diff(sort(rnorm(n))))}
R> hist(sapply(rep(10,999),func),col="gray")

This is *soooo* much better than having a loop!  Cheers everyone!
Anyone got any other interesting uses of sapply()?  Would anyone on
the List be interested in a collection specifically of neat R
oneliners?



-- 

Robin Hankin, Lecturer,
School of Geographical and Environmental Science
Private Bag 92019 Auckland
New Zealand

r.hankin at auckland.ac.nz
tel 0064-9-373-7599 x6820; FAX 0064-9-373-7042
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