On Apr 3, 2011, at 1:22 PM, Douglas Bates wrote:
On Sun, Apr 3, 2011 at 11:42 AM, David Winsemius <[email protected] > wrote:On Apr 3, 2011, at 12:14 PM, Samuel Le wrote:Dear all,I would like to log the calls to my functions. I am trying to do thisusing the function match.call():fTest<-function(x) { theCall<-match.call() print(theCall) return(list(x=x, logf = theCall)) }fTest(x=2)$x[1] 2fTest(x=2)$logffTest(x = 2)str(fTest(x=2)$logf)language fTest(x = 2)You may want to convert that call component to a character object, since:cat(fTest(x=2)$logf)Error in cat(list(...), file, sep, fill, labels, append) : argument 1 (type 'language') cannot be handled by 'cat'If you want to examine a call object you need to ensure that it is not evaluated. Evaluating a number or a character string is not a problem because eval(4) is the same as 4 However, evaluating a function call should be different from the call itself. As David shows, the str function is careful not to evaluate the call object. (Martin and I found ourselves going around in circles when looking at the structure of a fitted model object that included a call and he kindly changed the behavior of str().) So you need to decide when a function, such as print(), evaluates its arguments or when it doesn't, which can get kind of complicated. An alternative is to use match.call() repeatedly instead of trying to save the value, as infTestfunction(x) { print(match.call()) list(x=x, logf = match.call()) }fTest(x=2)fTest(x = 2) $x [1] 2 $logf fTest(x = 2) The trick there is that the value of match.call() is the unevaluated call whereas myCall <- match.call() print(myCall) evaluates myCall in the call to print, thereby evaluating the function fTest again. Is this sufficiently confusing? :-)
Yes, I am now sufficiently confused^W , ... er, motivated to look for another route. I think the way out of the confusion is to turn the call into text and since as.character doesn't do a very neat a job, I would suggest instead: deparse()
> fTest <- function(x) {
+ print(match.call())
+ list(x=x, logf = deparse(match.call()))
+ }
> fTest(x=3)$logf
fTest(x = 3)
[1] "fTest(x = 3)"
> cat(fTest(x=3)$logf)
fTest(x = 3)
fTest(x = 3)
cat() is a convenient test of the capacity of an object to be written
to a file. It has an append parameter that implies it could serve the
logging function requested by the OP.
I can see "theCall" printed into the console, but I don't manage to convert it into a character to write it into a log file with other informations. Can anyone help?
David Winsemius, MD West Hartford, CT ______________________________________________ [email protected] 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.
