[R] problem with input of integrate function

[David Winsemius]

On Jun 16, 2013, at 7:15 PM, David Winsemius wrote:

> 
> On Jun 16, 2013, at 6:46 PM, cassie jones wrote:
> 
>> Dear R-users,
>> 
>> I am trying to integrate a function using integrate command in R.
>> The function is as follows,
>> 
>> integrand
>> function(x,a)
>> {
>> exp(-0.5*a*(1+x^2))/(1+x^2)
>> }
>> 
>> Now while I want to integrate it using the command integrate, I get the
>> following error,
>> 
>> integrate(integrand(x,2),0,inf)
>> 
>> Error in match.fun(f) :
>> 'integrand(x, 2)' is not a function, character or symbol
>> 
>> I understand that the argument of integrate needs to be solely dependent on
>> x, that is why it is not able to recognize the input as there are both x
>> and a. But I need to have the integrand dependent on the variable a. Does
>> anyone know how can I handle the problem? Any help is appreciated.
> 
> You also misspelled `Inf`
> 
>> integrand <- function(x,a=2)
> + {
> + exp(-0.5*a*(1+x^2))/(1+x^2)
> + }
>> 
>> integrate(integrand,0,Inf)
> 0.247085 with absolute error < 3e-05

Can also use '..." argument:

?integrate

 integrand <- function(x,a)
 {
 exp(-0.5*a*(1+x^2))/(1+x^2)
 }
 
 integrate(integrand,0,Inf, a=2)
# 0.247085 with absolute error < 3e-05
> 
> 
>> 
>> Thanks in advance.
>> 
>> -Cassie
>> 
>> 	[[alternative HTML version deleted]]
>> 
>> ______________________________________________
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>> 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
> Alameda, CA, USA
> 
> ______________________________________________
> 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
Alameda, CA, USA