[R] Adapt function

[Ravi Varadhan]

Harold,

Try this:

ff <- function(x) x[1]*x[2]^2

adapt(2, lo = c(0,0), up = c(1,2), fun = ff)

The answer should be 4/3, since the first variable is integrated from 0 to 1 and the second variable (second-degree) is integrated from 0 to 2.

The answer is 1/3, if you do, 

adapt(2, lo = c(0,0), up = c(2,1), fun = ff)


Ravi.

____________________________________________________________________

Ravi Varadhan, Ph.D.
Assistant Professor,
Division of Geriatric Medicine and Gerontology
School of Medicine
Johns Hopkins University

Ph. (410) 502-2619
email: rvaradhan at jhmi.edu


----- Original Message -----
From: "Doran, Harold" <HDoran at air.org>
Date: Thursday, October 8, 2009 1:14 pm
Subject: [R] Adapt function
To: r-help at r-project.org


> I am trying to use the adapt function in the package adapt. To make sure
> I am using it correctly, I am trying a toy example that should yield a
> result of 2/3.
> 
> Suppose the function is f(x,y) = x*y^2 and I want to integrate over f 
> as
> 
> Int_0^1 Int_0^2 x*y^2 dxdy
> 
> Where the limits of integration for y are 0 to 1 and the limits for x
> are 0 to 2. So, I tried 
> 
> ff <- function(xy) x*y^2
> adapt(2, lo = c(0,0), up = c(1,2), fun = ff)
> 
> And this produces
> 
> > adapt(2, lo = c(0,0), up = c(1,2), fun = ff)
>       value      relerr      minpts      lenwrk       ifail 
>           2 7.38275e-08         165          73           0 
> 
> Can anyone offer insight into my error?
> 
> Harold
> 
> 
> 
> > sessionInfo()
> R version 2.9.0 (2009-04-17) 
> i386-pc-mingw32 
> 
> locale:
> LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
> States.1252;LC_MONETARY=English_United
> States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252
> 
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
> 
> 
> other attached packages:
> [1] adapt_1.0-4
> 
> loaded via a namespace (and not attached):
> [1] tools_2.9.0
> 
> ______________________________________________
> R-help at r-project.org mailing list
> 
> PLEASE do read the posting guide 
> and provide commented, minimal, self-contained, reproducible code.