On Tue, Dec 15, 2009 at 2:34 PM, Peng Yu <pengyu...@gmail.com> wrote: > 2009/12/15 <tlum...@u.washington.edu>: >> On Wed, 16 Dec 2009, Peng Yu wrote: >> >>> On Tue, Dec 15, 2009 at 10:32 PM, hadley wickham <h.wick...@gmail.com> >>> wrote: >>>>> >>>>> I don't understand what these addresses mean. Would you please help me >>>>> understand it? >>>> >>>> Did you try reading the documentation? >>>> >>>> When an object is traced any copying of the object by the C >>>> function ‘duplicate’ or by arithmetic or mathematical operations >>>> produces a message to standard output. The message consists of >>>> the string ‘tracemem’, the identifying strings for the object >>>> being copied and the new object being created, and a stack trace >>>> showing where the duplication occurred. ‘retracemem()’ is used to >>>> indicate that a variable should be considered a copy of a previous >>>> variable (e.g. after subscripting). >>> >>> "The message consists of the string ‘tracemem’, the identifying >>> strings for the object being copied and the new object being created, >>> and a stack trace showing where the duplication occurred." >>> >>> I tried to read the document before I posted, but wasn't be able to >>> understand it, because there are multiple ways to parse it. >>> >>> To make sure that I understand, I rewrite the above sentence to the >>> following. Is it correct? >>> >>> "The message consists of the string ‘tracemem’, the string indicating >>> the object being copied, the string indicating the new object being >>> created, and a stack trace showing where the duplication occurred." >>> >>> I also didn't see a stack trace in my example. If I didn't see Martin >>> Morgan's post, I will still be confused. >>> >> >> The stack trace is there, it's just that it is empty because you aren't in a >> function. >> >>> I thought that there should be only one coping. Why there are two lines? >>> >>> tracemem[0x05cf2798 -> 0x05cf2750]: >>> tracemem[0x05cf2750 -> 0x05ed8ba0]: > > I still don't understand what the numbers after 'tracemem[' are. Could > somebody please explain it? > >> x=1:3 >> tracemem(x) > [1] "<0x1056ef8>" >> x[[4]]=8#I still don't understand what '0x9ac9f0' means here > tracemem[0x1056ef8 -> 0x9ac9f0]: >> tracemem(x)#The address of 'x' is 0x9aca38 but not '0x9ac9f0' > [1] "<0x9aca38>"
Hi Thomas, The address of x after 'x[[4]]=8' is '0x9ac9f0'. Why the last 'tracement(x)' gives '0x9aca38'? >> There are two lines because there are two copies. One is the lazy copy >> because the object is modified, the other is because it is converted from >> integer to numeric. >> >> The whole point of tracemem() is to show copies that you didn't expect, so >> being surprised by it is a good thing. >> >> -thomas >> >> Thomas Lumley Assoc. Professor, Biostatistics >> tlum...@u.washington.edu University of Washington, Seattle >> > ______________________________________________ R-help@r-project.org 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.
