problem with input of integrate function

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

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problem with input of integrate function

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