[R] two-dimensional integration?

[Dimitris Rizopoulos]

This existed even before the Athens Olympics 2004 :)

look at package "adapt" which integrates a function from 2 to 20 
dimensions, e.g.,

library(adapt)
f <- function(x){
    x1 <- x[1]
    x2 <- x[2]
    sin(x1*x2)*exp(x1-x2)
}

adapt(2, c(0,0), c(1,1), functn=f)

I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/
     http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Nils-at-Duke Lid Hjort" <hjort at isds.duke.edu>
To: <R-help at stat.math.ethz.ch>; <nils at math.uio.no>
Sent: Thursday, March 10, 2005 6:22 AM
Subject: [R] two-dimensional integration?


>I find the one-dimensional "integrate" very helpful,
> but often enough I stumble into problems that require
> two (or more)-dimensional integrals. I suppose there
> are no R functions that can do this for me, "directly"?
>
> The ideal thing would be to be able to define say
> f <- function(x)
> {
> x1 <- x[1]
> x2 <- x[2]
> sin(x1*x2)*exp(x1-x2)
> }
> and then write say
> integrate(f, xlim=c(0,1), ylim=c(0,1))  .
>
> (a) No such thing exists, as of today, right?
> (b) There *are* general numerical routines "out there"
> for doing such things, right? (Importance sampling
> or adaptive important sampling would often do the
> job, but it would be difficult to find something that
> "always" works -- at least in higher dimension?
> Also, iterated one-dimensional integrations could
> be attempted, but I find that messy, also because
> things lose the g(many) = many(g) property, and
> then R refuses to integrate g.)
> (c) Will a thing like the above exist in R before
> the Tromsoe Olympics in 2014? For which dimensions?
> Nils Lid Hjort
> [Professor of statistics at Oslo, but currently at Duke]
>
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