On Jun 24, 2011, at 11:10 AM, Ravi Varadhan wrote:

Thank you very much, Jim.  That works!

I did know that I could process the character strings using regex, but was also wondering if there was a direct way to get this.

Suppose, in the current example I would like to obtain a 3-column matrix that contains the parameters and the function value:

fr <- function(x) {   ## Rosenbrock Banana function
   on.exit(print(cbind(x1, x2, f)))
   x1 <- x[1]
   x2 <- x[2]
   f <- 100 * (x2 - x1 * x1)^2 + (1 - x1)^2
   f    
}

fvals <- capture.output()

Now, I need to tweak your solution to get the 3-column matrix.

I don't understand "the 3 column matrix" part of your request. Are you asking for something that is not printed to the console? I only get a sequence of single element vectors at my console when I execute:

ans <- optim(c(-1.2,1), fr)

It would be nice, if there was a more direct way to get the numerical output, perhaps a numeric option in capture.output().

But maybe Snow's answer is a complete solution.


Best,
Ravi.


--
David Winsemius, MD
West Hartford, CT

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