[R] help with likelihood contour plot

[Sundar Dorai-Raj]

Murray Jorgensen wrote:
> Can some kind person point out my error here? I'm trying to set up a 
> grid for a countour plot of a likelihood function.
> 
>  > u <- rnorm(20,9.5,2.5)
>  > # sample of size 20 from N(9.5,2.5^2)
>  > loglik <- function(th1,th2) {
> + n <- length(u)
> + -(n/2)*log(2*pi*th2^2)-0.5*sum((u-th1)^2/th2^2)
> + }
>  > x <- seq(4.5,14.5,len=50)
>  > y <- seq(0.5,6,len=50)
>  > f <- outer(x, y, loglik(x,y))
> Error in match.fun(FUN) : not function, character, or symbol: "loglik(x, 
> y)"
> In addition: Warning message:
> longer object length
>         is not a multiple of shorter object length in: u - th1
>  > loglik(9,2)
> [1] -44.56294
>  > is.function(loglik)
> [1] TRUE
> 
> Thanks,
> 
> Murray


Murray,
   From ?outer:

Details:

      `FUN' must be a function (or the name of it) which expects at
      least two arguments and which operates elementwise on arrays.


Thus, use "loglik" and not "loglik(x,y)", as in:

outer(x,y,loglik)

Regards,
Sundar