R help - Feb 2013 - integrate function

Hi All,

Can any one help to explain why min and max function couldn't work in the
integrate function directly.

For example, if issue following into R:

integrand <- function(x) {min(1-x, x^2)}
integrate(integrand, lower = 0, upper = 1)

it will return this:
Error in integrate(integrand, lower = 0, upper = 1) :
  evaluation of function gave a result of wrong length


However, as min(U,V) = (U+V)/2-abs(U-V)/2

Below code working;

integrand <-
function(x){(1-x+x^2)/2-0.5*abs(1-x-x^2)}
> integrate(integrand, lower = 0, upper = 1)
0.151639 with absolute error < 0.00011

I am confused...


Dan

	[[alternative HTML version deleted]]

use pmin instead of min.
hth
Matthias

On 12.02.2013 16:41, dan wang wrote:
> Hi All,
>
> Can any one help to explain why min and max function couldn't work in
the
> integrate function directly.
>
> For example, if issue following into R:
>
> integrand <- function(x) {min(1-x, x^2)}
> integrate(integrand, lower = 0, upper = 1)
>
> it will return this:
> Error in integrate(integrand, lower = 0, upper = 1) :
>    evaluation of function gave a result of wrong length
>
>
> However, as min(U,V) = (U+V)/2-abs(U-V)/2
>
> Below code working;
>
> integrand <- function(x){(1-x+x^2)/2-0.5*abs(1-x-x^2)}
>> integrate(integrand, lower = 0, upper = 1)
> 0.151639 with absolute error < 0.00011
>
> I am confused...
>
>
> Dan
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>
-- 
Prof. Dr. Matthias Kohl
www.stamats.de

integrate() want a vectorized function, one such that length(f(x))==length(x).
Use pmin or pmax instead of min or max.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org] On Behalf
> Of dan wang
> Sent: Tuesday, February 12, 2013 7:41 AM
> To: r-help at r-project.org
> Subject: [R] integrate function
> 
> Hi All,
> 
> Can any one help to explain why min and max function couldn't work in
the
> integrate function directly.
> 
> For example, if issue following into R:
> 
> integrand <- function(x) {min(1-x, x^2)}
> integrate(integrand, lower = 0, upper = 1)
> 
> it will return this:
> Error in integrate(integrand, lower = 0, upper = 1) :
>   evaluation of function gave a result of wrong length
> 
> 
> However, as min(U,V) = (U+V)/2-abs(U-V)/2
> 
> Below code working;
> 
> integrand <- function(x){(1-x+x^2)/2-0.5*abs(1-x-x^2)}
> > integrate(integrand, lower = 0, upper = 1)
> 0.151639 with absolute error < 0.00011
> 
> I am confused...
> 
> 
> Dan
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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.