[Rd] suggested modification to the 'mle' documentation?

[Peter Dalgaard]

Spencer Graves wrote:
> Hello: 
>
>       I wish to again express my appreciation to all who have 
> contributed to making R what it is today. 
>
>       At this moment, I'm particularly grateful for whoever modified the 
> 'mle' code so data no longer need be passed via global variables.  I 
> remember struggling with this a couple of years ago, and I only today 
> discovered that it is no longer the case. 
>
>       I'd like to suggest that the 'mle' help file be modified to 
> advertise this fact, e.g., by adding one of the two examples appearing 
> below. 
>   

In a word: No!!! That is not the design. A likelihood function is a 
function of its parameters, and the "fixed" argument is for holding some 
parameters fixed (e.g. during profiling).

To include data, just make a closure, e.g.

poissonLike <- function(x., y.){
    function(ymax=15, xhalf=6)
      -sum(stats::dpois(y., lambda=ymax/(1+x./xhalf), log=TRUE))}
mll <-  poissonLike(x, y)
mle(ll, ....


>       Best Wishes,
>       Spencer Graves
> ################################
> x <- 0:10
> y <- c(26, 17, 13, 12, 20, 5, 9, 8, 5, 4, 8)
> #  Pass data via function arguments rather than global variables
> ll.5 <- function(ymax=15, xhalf=6, x., y.)
>          -sum(stats::dpois(y., lambda=ymax/(1+x./xhalf), log=TRUE))
> (fit.5 <- mle(ll.5, start=list(ymax=15, xhalf=6),
>               fixed=list(x.=x, y.=y)))
>
> ll3 <- function(lymax=log(15), lxhalf=log(6), x., y.)
>   -sum(stats::dpois(y.,
>          lambda=exp(lymax)/(1+x./exp(lxhalf)), log=TRUE))
> (fit3 <- mle(ll3, start=list(lymax=0, lxhalf=0),
>              fixed=list(x.=x, y.=y)))
>
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>   


-- 
   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
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