It is sure thing that different person has different expectation of the help system. Personally, I think Stata's on-line help system is too brief, though the manual may be a different story. Perhaps, it is all about the habit and the extent to which you are used to (and how much you know about it).
2009/4/17 Stas Kolenikov <skole...@gmail.com>: > See, we just jave different expectations of what is to be seen in the > help system, and are used to different formats. Yes, Stata thinks of > data as a rectangular array (although it stores it in memory, unlike > SAS). The inputs to -egen-, as well as the values produced, depend on > the particular function -fcn- and are described in subsections on > those individual functions. That is mentioned at the top of the page. > There is a pretty much standard syntax of most Stata commands (command > name followed by variables it is applied to or expression to be > computed followed by if conditions on observations followed by comma > options ), and -egen- more or less satisfies that syntax. A Stata user > equipped with the basic concepts of the assignment command -generate- > (which -egen- is said to extend) and variable lists (-varlist- here > and there in the help file) would be able to make sense of this all. > > I would rather translate R's ave() to Stata's -by- expression. Not all > of the -egen- functionality can be implemented via ave(). > > Looks like terseness is a prerequisite to doing anything in R though. > If I am telling you I am a newbie, the book abbreviations although > standard to everybody on this list may not mean much to me. I could > figure out "Regression Modeling Strategies" (although I was not > thinking about it as a book on R -- I probably did not read it far > enough :) ), and V&R is Venables & Ripley. Right? > > On 4/16/09, David Winsemius <dwinsem...@comcast.net> wrote: >> Terse is OK by me as long as I get told what goes in (allowable data types, >> argument names and effects) and what comes out. What seemed to be lacking in >> that Stata doc for egen was a description of the purpose or behavior and >> then could find no description of the values produced. Perhaps it is because >> Stata has an approach that everything is a rectangular array? Is everything >> assumed to create a new column of data as in SAS? >> >> At any rate it looked to this casual non-user, reading that document, that >> egen creates a new variable aligned with its argument variables by applying >> various functions within groupings. That is pretty much what ave does. "ave" >> is not restricted to mean as a functional argument. As I said it was a >> guess. >> >> The texts I used to get up to speed in R are several downloaded from the >> Contributed documents (including anything written by Venables), V&R MASS v >> 2, Harrell's RMS, Sarkar's Lattice, Chambers&Hastie SMiS and reading a lot >> of Q&A on this list. >> >> -- >> David Winsemius >> >> On Apr 16, 2009, at 11:57 AM, Stas Kolenikov wrote: >> >> >> > http://www.stata.com/help.cgi?egen -- it creates new >> variables dealing >> > with some special relatively non-standard tasks that don't boil down >> > to a one-line arithmetic expressions. For that reason, there will be >> > no equivalent to -egen- in general, as it has so many functions that >> > are so different. -rowtotal- is of course just a shorthand for sum(), >> > except for treatment of missing values ( ifelse(is.na(x),0,x ). But >> > -anycount- is a moderately complicated double cycle over variables and >> > list of values (40 lines of underlying Stata code, including parsing >> > and labeling the resulting variables)... which will probably become a >> > triple R cycle including the cycle over observations, although the >> > latter can probably be avoided. >> > >> > Yes, R documentation looks exteremely terse to me as a regular Stata >> > user. I am used to seeing the concpets explained well, even in the >> > help files, and certainly more so in the shelved books. As every >> > option and every part of the syntax is devoted at least three to five >> > sentences, and the most common uses are exemplified, I can usually >> > figure out how to run a particular task relatively quickly. (The data >> > management tricks, which is what Peter was asking about above, are >> > probably an exception: you either know them, or you don't. In this >> > example, I don't know the corresponding R tricks, although I can >> > probably brute force the solution if I needed to.) The fraction of >> > commands in R that I personally have been coming across that are >> > comparably well documented is about a quarter. For other, it is either >> > a guesswork+CRANning+googling around or "Forget it, I'll just go back >> > to Stata to do it" after a few futile attempts. May be I just don't >> > know where to look for the good stuff, but it is certainly outside R >> > as a package+its documentation. >> > > > -- > Stas Kolenikov, also found at http://stas.kolenikov.name > Small print: I use this email account for mailing lists only. > > ______________________________________________ > 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. > -- HUANG Ronggui, Wincent PhD Candidate Dept of Public and Social Administration City University of Hong Kong Home page: http://asrr.r-forge.r-project.org/rghuang.html ______________________________________________ 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.
