R help - Jun 2008 - try to find the MLE of a function

Hi everyone:
    I have a density function f(x|theta)=theta*x^(theta-1),where
0<x<1,0<theta<infinite

I want to pratice on R to find the MLE of this function,here is my code:
    x <- (0:10)/10
f<-function(theta) prod(theta*x^(theta-1))
mle(f)
and r gave me :Error in eval(expr, envir, enclos) : argument is missing,
with no default

what mistake I just made?and how to add a constraint of theta>0 in my
function.

Great thanks for your time~

	[[alternative HTML version deleted]]

Hi,

mle caused me some confusion too.

Anyway, first of all, your x should not contain 0, so make it, let say,
(1:10)/10.
Secondly, f should not be the density, but -log(density), so in your case it
should be
f <-function(theta) -sum(log(theta) + (theta-1)*log(x))

and finally you must specify a start value, i.e. your call should be
mle(f,start=list(thetha=1))


--- On Thu, 19/6/08, Manli Yan <manliyanrhelp at gmail.com> wrote:
> From: Manli Yan <manliyanrhelp at gmail.com>
> Subject: [R] try to find the MLE of a function
> To: "r-help at r-project.org" <r-help at r-project.org>
> Received: Thursday, 19 June, 2008, 1:49 PM
> Hi everyone:
>     I have a density function
> f(x|theta)=theta*x^(theta-1),where
> 0<x<1,0<theta<infinite
> 
> I want to pratice on R to find the MLE of this
> function,here is my code:
>     x <- (0:10)/10
> f<-function(theta) prod(theta*x^(theta-1))
> mle(f)
> and r gave me :Error in eval(expr, envir, enclos) :
> argument is missing,
> with no default
> 
> what mistake I just made?and how to add a constraint of
> theta>0 in my
> function.
> 
> Great thanks for your time~
> 
> 	[[alternative HTML version deleted]]
> 
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