[R] cdf

[David Winsemius]

On Oct 13, 2009, at 5:12 PM, maram salem wrote:

> Dear all,
> I have the cdf of the following power fuction distribution:
> F(y)=(y/350)^a               ,0<y<350,
> where " a " is some parameter with range a>0.
> I want to use it as the argument of the discretize function of the  
> actuar package.
>
> So I think I need to define this function to R so that if I entered  
> a=1, I get the following
> F(y)=(y/350)
> and if I entered a=4.5, I get the following
> F(y) =(y/350)^4.5
> ........... and so on
>
> I've tried
> a<-vector(mode="numeric",length=1)
> powercdf<-function(a,y)
> (y/350)^a
>
> But when I typed: powercdf(10,y)
> instead of getting : (y/350)^10     (which is what I want)
> I got : object y not found ??
>
> I want y to remain as it is, a continous variable, not for example  
> seq(0,350).
> Thank you in advance.

If you want symbolic algebra then use a system designed for such. If  
you invoke a function in R you need to give it arguments for  
evaluation  ... to numerical values.

If you want a function that returns a function, that is also possible.

 > cdffn <- function(y, arg) return( function(y) {y^arg} )
 > cdf10 <- cdffn(y, 10)
 > cdf10(1:10)
  [1]           1        1024       59049     1048576     9765625     
60466176   282475249  1073741824
  [9]  3486784401 10000000000


David Winsemius, MD
Heritage Laboratories
West Hartford, CT