[R] Integration subroutine?

[Liaw, Andy]

The function need to be vectorized.  Try:

> fr2.new <- function(x) ifelse(x < 1, x * x, 1)
> integrate(fr2.new, -1, 2) 
1.666667 with absolute error < 3.4e-05

Andy

From: Lynette Sun
> 
> Hi all,
> 
> Why 
> 
> fr2<-function(x)
> { if(x<1){x*x}else{1}
> }
> 
>  integrate(fr2,-1,2) 
> 
> gives the following wrong answer:
> 
> 3 with absolute error < 3.3e-14
> Warning message: 
> the condition has length > 1 and only the first element will 
> be used in: if (x < 1) { 
> 
> while
> 
> fr<-function(x){as.numeric(x<1)*(x^2-1)+1}
> 
>  integrate(fr,-1,2)    
> 
> works?
> 
> 1.666667 with absolute error < 3.4e-05
> 
> Thanks.
> 
> 
> Lynette Sun
> 
> Department of Statistics
> 
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> 
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