Re: [R] Help in Optimization of a function

2012-07-08 Thread peter dalgaard
On Jul 8, 2012, at 16:52 , John C Nash wrote: > This looks like a homework trap set up to catch those trying to use > facilities like Rhelp. > > f = exp(x^2-y+z^(-1))= exp(x^2) * exp(1/z)/exp(y) > > To maximize clearly needs biggest x (37), smallest y (2) and a z that > makes exp(1/z) big -- 0

[R] Help in Optimization of a function

2012-07-08 Thread John C Nash
gt; Date: Sun, 8 Jul 2012 10:15:34 +0100 > From: Raghuraman Ramachandran > To: R Project Help > Subject: [R] Help in Optimization of a function > Message-ID: > > Content-Type: text/plain > > guRus! > > I have a function f = exp(x^2-y+(1/z)) > > Also,

Re: [R] Help in Optimization of a function

2012-07-08 Thread Rui Barradas
Hello, There are several optimization functions in R. There's even a group dedicated to the field. See the CRAN Task View: Optimization and Mathematical Programming. To use optim(), you could do something like f <- function(x, y, z) (x^2 - y - z^2/2) # I've changed the function negf <- funct

Re: [R] Help in Optimization of a function

2012-07-08 Thread Rui Barradas
Hello, You don't need an optimzation routine to know that the maximum of this function is +Inf. It's attained at z = 0+ (when z converges to zero by positive values). This breaks the R function optim(), by the way. It " needs finite values of 'fn' " Hope this helps, Rui Barradas Em 08-07-

[R] Help in Optimization of a function

2012-07-08 Thread Raghuraman Ramachandran
guRus! I have a function f = exp(x^2-y+(1/z)) Also, x can take values from 1 to 37, y from 2 to 20 and Z from -13 to 51. How can I find the maximum of f using any of the optimization functions please? Is there a way to store the possible values of x, y and Z in a single variable like in a List