[R] nlm() problem : extra parameters

[Gabor Grothendieck]

Change the name of n to something else.  Also please using spacing
in your code for readability.

> x <- c(10.2, 7.7, 5.1, 3.8, 2.6)
> y <- c(9, 8, 3, 2, 1)
> n. <- c(10, 9, 6, 8, 10)
>
>
> derfs4 <- function(b, x, y, n.)
+ {
+          b0 <- b[1]
+          b1 <- b[2]
+          c=b0 +b1 * x
+          d <- exp(c)
+          p= d/(1+d)
+          e <- d/(1+d)^2
+          f  <- - sum(log(choose(n., y)) - n. * log(1 + d) + y * c)
+          attr(f, "gradient") <- c(- sum(y - n. * p), -sum(x * (y - n. * p)))
+          attr(f, "hessian") <- matrix(c(sum(n. * e), sum(n. * x * e),
+               sum(n. * x * e), sum(n. * x^2 * e)), 2, 2)
+          return(f)
+ }
>
>
> nlm(derfs4, c(-3.9, 0.64), hessian = TRUE, x = x, y = y, n. = n.)
$minimum
[1] 5.746945

$estimate
[1] -3.5380638  0.6505037

$gradient
[1] -0.031425476 -0.006637742

$hessian
          [,1]      [,2]
[1,]  5.963954  31.15266
[2,] 31.152658 192.53408

$code
[1] 4

$iterations
[1] 100



On 3/2/07, Mervyn G Marasinghe <mervyn at iastate.edu> wrote:
> Hello:
>
> Below is a toy logistic regression problem. When I wrote my own code,
> Newton-Raphson converged in three iterations using both the gradient
> and the Hessian  and the starting values  given below. But I can't
> get nlm() to work! I would much appreciate any help.
>
>  > x
> [1] 10.2  7.7  5.1  3.8  2.6
>  > y
> [1] 9 8 3 2 1
>  > n
> [1] 10  9  6  8 10
>
>
> derfs4=function(b,x,y,n)
> {
>          b0 = b[1]
>          b1 = b[2]
>          c=b0+b1*x
>          d=exp(c)
>          p=d/(1+d)
>          e=d/(1+d)^2
>          f  = -sum(log(choose(n,y))-n*log(1+d)+y*c)
>          attr(f,"gradient")=c(-sum(y-n*p),-sum(x*(y-n*p)))
>          attr(f,"hessian")=matrix(c(sum(n*e),sum(n*x*e),sum(n*x*e),sum(n*x^2*e)),2,2)
>          return(f)
> }
>
>
>  > nlm(derfs4,c(-3.9,.64),hessian=T,print.level=2,x=x,y=y,n=n)
> Error in choose(n, y) : argument "n" is missing, with no default
>  >
> I tried a variety of other ways  too.  When I got it to work it did not
> converge in 100 iterations ;rather like the fgh example given on the lme
> help page.
>
> Mervyn
>
>
>        [[alternative HTML version deleted]]
>
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>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>