Here is one approach (different from capture.output) that I believe
accomplishes what you are trying to do:
frtop <- function(){
out <- numeric(0)
topenv <- environment()
fr <- function(x) { ## Rosenbrock Banana function
x1 <- x[1]
x2 <- x[2]
f <- 100 * (x2 - x1 * x1)^2 + (1 - x1)^2
topenv$out <- c(topenv$out, f)
f
}
ans <- optim(c(-1.2,1), fr)
list(ans=ans, out=out)
}
out <- frtop()
Now out is a list with 2 components, the first is the return value from optim,
the second is a vector with all the f values from the evaluation of the fr
function.
The basic idea is to wrap everything in a toplevel function, so that it has its
own local environment, then define the out vector in the toplevel environment.
We also have a link to that environment through the topenv variable. Now fr is
defined inside of frtop so it can access that environment (lexical scoping) and
so when we assign to topenv$out it is doing the assignment in the environment
of frtop. Then we just run optim which calls fr a bunch of times, then output
a list with the output and the values at each call.
Hope this helps,
-----Original Message-----
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
Behalf Of Ravi Varadhan
Sent: Friday, June 24, 2011 8:40 AM
To: r-help@r-project.org
Subject: [R] How to capture console output in a numeric format
Hi,
I would like to know how to capture the console output from running an
algorithm for further analysis. I can capture this using capture.output() but
that yields a character vector. I would like to extract the actual numeric
values. Here is an example of what I am trying to do.
fr <- function(x) { ## Rosenbrock Banana function
on.exit(print(f))
x1 <- x[1]
x2 <- x[2]
f <- 100 * (x2 - x1 * x1)^2 + (1 - x1)^2
f
}
fvals <- capture.output(ans <- optim(c(-1.2,1), fr))
Now, `fvals' contains character elements, but I would like to obtain the actual
numerical values. How can I do this?
Thanks very much for any suggestions.
Best,
Ravi.
-------------------------------------------------------
Ravi Varadhan, Ph.D.
Assistant Professor,
Division of Geriatric Medicine and Gerontology School of Medicine Johns Hopkins
University
Ph. (410) 502-2619
email: rvarad...@jhmi.edu<mailto:rvarad...@jhmi.edu>
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