R help - Mar 2011 - integrate a fuction

I'm having a function of the form

1> f<-function(x){
1+ 
1+    return(x^p)
1+ 
1+ }

,and I would like to integrate it with respect to x, where p should be any
constant.

One way would be to set a value for p globally and then call integrate
function: 
p=2
integrate(f, lower = -1, upper = 1)

However, I would like to use 'integrate' inside a function, so I  could
call
it passing p as a parameter. I tried something like this:

1> p=1
1> integral<-function(p){
1+    integrate(f, lower = -1, upper = 1)
1+ 
1+ }
1> 
1> integral(2)
0 with absolute error < 1.1e-14

,but it doesn't work as the integral of f is evaluated with p=1 (the value
of the global variable p) and not with the value of p=2 when the function
integral is called.

Does anyone knows how can I solve this problem?
Thanks in advance
santiagorf



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On Mar 4, 2011, at 6:01 PM, santiagorf wrote:
> I'm having a function of the form
>
> 1> f<-function(x){
> 1+
> 1+    return(x^p)
> 1+
> 1+ }
>
> ,and I would like to integrate it with respect to x, where p should  
> be any
> constant.
>
> One way would be to set a value for p globally and then call integrate
> function:
> p=2
> integrate(f, lower = -1, upper = 1)
>
> However, I would like to use 'integrate' inside a function, so I   
> could call
> it passing p as a parameter. I tried something like this:
>
> 1> p=1
> 1> integral<-function(p){
> 1+    integrate(f, lower = -1, upper = 1)
> 1+
> 1+ }
> 1>
> 1> integral(2)
> 0 with absolute error < 1.1e-14
>
> ,but it doesn't work as the integral of f is evaluated with p=1 (the  
> value
> of the global variable p) and not with the value of p=2 when the  
> function
> integral is called.
Functions carry with them environments in whaich they are defined.
>
> Does anyone knows how can I solve this problem?

Build `f` to have two parameters.

-- 
David
> Thanks in advance
> santiagorf
>
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/integrate-a-fuction-tp3336066p3336066.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

If f is a two-parameter function, how can I integrate it with respect to p?

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I received the solution...

Hi:

This is what David means:

f <- function(x, p) x^p

integrate(f, lower = -1, upper = 1, p = 2)
0.6666667 with absolute error < 7.4e-15
integrate(f, lower = -1, upper = 1, p = 3)
0 with absolute error < 5.6e-15                 # this is correct

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