Re: [R] round() and negative digits
On 11/10/11 08:17, Michael Friendly wrote: On 10/9/2011 6:18 AM, Prof Brian Ripley wrote: Sometimes it is better not to document things than try to give precise details which may get changed *and* there will be useRs who misread (and maybe even file bug reports on their misreadings). The source is the ultimate documentation. I can't agree with this less. The source does the computation. The documentation says how to use it and what it should do. Corner cases can be trapped in code or mentioned in Notes. But the source is only useful if you can easily find it and then can understand what it is doing, particularly for a .Primitive like round(). The source is only the documentation of last resort. I agree. It seems to me that saying that the source is the ultimate documentation is rather like (in pure mathematics) saying that all maths follows from the Zermello-Fraenkel axioms plus the Axiom of Choice, so those axioms are all that we need to tell anyone. cheers, Rolf Turner __ 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.
Re: [R] round() and negative digits
On 11-10-11 7:14 PM, Rolf Turner wrote: On 11/10/11 08:17, Michael Friendly wrote: On 10/9/2011 6:18 AM, Prof Brian Ripley wrote: Sometimes it is better not to document things than try to give precise details which may get changed *and* there will be useRs who misread (and maybe even file bug reports on their misreadings). The source is the ultimate documentation. I can't agree with this less. The source does the computation. The documentation says how to use it and what it should do. Corner cases can be trapped in code or mentioned in Notes. But the source is only useful if you can easily find it and then can understand what it is doing, particularly for a .Primitive like round(). The source is only the documentation of last resort. I agree. It seems to me that saying that the source is the ultimate documentation is rather like (in pure mathematics) saying that all maths follows from the Zermello-Fraenkel axioms plus the Axiom of Choice, so those axioms are all that we need to tell anyone. R is an open source project. That means we expect people to look at the source, to answer some of their own questions, to suggest improvements, to point out errors. If you don't look at it, you aren't holding up your side of the bargain. Duncan Murdoch __ 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.
Re: [R] round() and negative digits
The source does not document intent. I, too disagree with Dr Ripley on this point. The library mechanism insists that some attempt at documentation be included with the source, for good reason. I would rather the documentation assert intent to support negative rounding values and later add the caveat that it may not be achievable in all cases than not mention the option at all. It is much easier to critique the code and documentation together than depend purely on the algorithmic expressions in the code... I may wonder if the author intended the code to have some odd corner case behavior in order to meet a performance goal. Documentation that addresses that helps, and documentation that doesn't may simply be mysterious. Documentation that disagrees with the code prompts repairs... of the code, or the documentation. --- Jeff Newmiller The . . Go Live... DCN:jdnew...@dcn.davis.ca.us Basics: ##.#. ##.#. Live Go... Live: OO#.. Dead: OO#.. Playing Research Engineer (Solar/Batteries O.O#. #.O#. with /Software/Embedded Controllers) .OO#. .OO#. rocks...1k --- Sent from my phone. Please excuse my brevity. Duncan Murdoch murdoch.dun...@gmail.com wrote: On 11-10-11 7:14 PM, Rolf Turner wrote: On 11/10/11 08:17, Michael Friendly wrote: On 10/9/2011 6:18 AM, Prof Brian Ripley wrote: Sometimes it is better not to document things than try to give precise details which may get changed *and* there will be useRs who misread (and maybe even file bug reports on their misreadings). The source is the ultimate documentation. I can't agree with this less. The source does the computation. The documentation says how to use it and what it should do. Corner cases can be trapped in code or mentioned in Notes. But the source is only useful if you can easily find it and then can understand what it is doing, particularly for a .Primitive like round(). The source is only the documentation of last resort. I agree. It seems to me that saying that the source is the ultimate documentation is rather like (in pure mathematics) saying that all maths follows from the Zermello-Fraenkel axioms plus the Axiom of Choice, so those axioms are all that we need to tell anyone. R is an open source project. That means we expect people to look at the source, to answer some of their own questions, to suggest improvements, to point out errors. If you don't look at it, you aren't holding up your side of the bargain. Duncan Murdoch _ 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. [[alternative HTML version deleted]] __ 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.
Re: [R] round() and negative digits
On 10/9/2011 6:18 AM, Prof Brian Ripley wrote: Sometimes it is better not to document things than try to give precise details which may get changed *and* there will be useRs who misread (and maybe even file bug reports on their misreadings). The source is the ultimate documentation. I can't agree with this less. The source does the computation. The documentation says how to use it and what it should do. Corner cases can be trapped in code or mentioned in Notes. But the source is only useful if you can easily find it and then can understand what it is doing, particularly for a .Primitive like round(). The source is only the documentation of last resort. -Michael __ 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.
Re: [R] round() and negative digits
On 09/10/11 00:18, Duncan Murdoch wrote: On 11-10-07 5:26 PM, Carl Witthoft wrote: Just wondering here -- I tested and found to my delight that % round(325.4,-2) [1] 300 gave me exactly what I would have expected (and wanted). Since it's not explicitly mentioned in the documentation that negative 'digits' is allowed, I just wanted to ask whether this behavior is intentional or a happy turn of events. I'm always paranoid that something not explicitly documented might disappear in future revisons. It is intentional, and one of the regression tests confirms that it's there, so it won't disappear by mistake, and would be very unlikely to disappear intentionally. Uh, wouldn't it be *nice* to mention this --- not completely obvious --- capability in the help file? cheers, Rolf __ 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.
Re: [R] round() and negative digits
On 09/10/11 10:39, Duncan Murdoch wrote: On 11-10-08 5:32 PM, Rolf Turner wrote: On 09/10/11 00:18, Duncan Murdoch wrote: On 11-10-07 5:26 PM, Carl Witthoft wrote: Just wondering here -- I tested and found to my delight that % round(325.4,-2) [1] 300 gave me exactly what I would have expected (and wanted). Since it's not explicitly mentioned in the documentation that negative 'digits' is allowed, I just wanted to ask whether this behavior is intentional or a happy turn of events. I'm always paranoid that something not explicitly documented might disappear in future revisons. It is intentional, and one of the regression tests confirms that it's there, so it won't disappear by mistake, and would be very unlikely to disappear intentionally. Uh, wouldn't it be *nice* to mention this --- not completely obvious --- capability in the help file? If we told you all of R's secrets, we'd have to kill you. Fortune nomination? cheers, Rolf __ 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.
Re: [R] round() and negative digits
On 09-Oct-11 00:46:58, Carl Witthoft wrote: On 10/8/11 6:11 PM, (Ted Harding) wrote: Carl Witthoft's serendipitous discovery is a nice example of how secrets can be guessed by wondering what if ... ?. So probably you don;t need to tell the secrets. Taking the negative digits to their logical extreme: round(654.321,2) # [1] 654.32 round(654.321,1) # [1] 654.3 round(654.321,0) # [1] 654 round(654.321,-1) # [1] 650 round(654.321,-2) # [1] 700 round(654.321,-3) # [1] 1000 round(654.321,-4) # [1] 0 which is what you'd logically expect (but is it what you would intuitively expect?). Oh, oh, somebody's going all metaphysical on us. Nor should one forget the rounding rules (not OS-dependent in this case, I think ... ?): round(5000,-4) # [1] 0 round(15000,-4) # [1] 2 Ted. E-Mail: (Ted Harding) ted.hard...@wlandres.net Fax-to-email: +44 (0)870 094 0861 Date: 09-Oct-11 Time: 08:59:58 -- XFMail -- __ 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.
Re: [R] round() and negative digits
On 11-10-09 4:00 AM, (Ted Harding) wrote: On 09-Oct-11 00:46:58, Carl Witthoft wrote: On 10/8/11 6:11 PM, (Ted Harding) wrote: Carl Witthoft's serendipitous discovery is a nice example of how secrets can be guessed by wondering what if ... ?. So probably you don;t need to tell the secrets. Taking the negative digits to their logical extreme: round(654.321,2) # [1] 654.32 round(654.321,1) # [1] 654.3 round(654.321,0) # [1] 654 round(654.321,-1) # [1] 650 round(654.321,-2) # [1] 700 round(654.321,-3) # [1] 1000 round(654.321,-4) # [1] 0 which is what you'd logically expect (but is it what you would intuitively expect?). Oh, oh, somebody's going all metaphysical on us. Nor should one forget the rounding rules (not OS-dependent in this case, I think ... ?): round(5000,-4) # [1] 0 round(15000,-4) # [1] 2 The intention is that those are not OS dependent, but since they rely on exact representations, there could be differences: not all platforms support the extended real 80 bit intermediate representations. (If you were rounding to 0 d.p., they should all agree on a round to even rule. Rounding to -4 d.p. involves dividing by 10^4, and that could lead to errors.) Duncan Murdoch __ 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.
Re: [R] round() and negative digits
On Sat, 8 Oct 2011, Duncan Murdoch wrote: On 11-10-07 5:26 PM, Carl Witthoft wrote: Just wondering here -- I tested and found to my delight that % round(325.4,-2) [1] 300 gave me exactly what I would have expected (and wanted). Since it's not explicitly mentioned in the documentation that negative 'digits' is allowed, I just wanted to ask whether this behavior is intentional or a happy turn of events. I'm always paranoid that something not explicitly documented might disappear in future revisons. It is intentional, and one of the regression tests confirms that it's there, so it won't disappear by mistake, and would be very unlikely to disappear intentionally. It needs careful documentation though (as do the corner cases of signif). Things like round(325.4,-3) [1] 0 signif(325.4,-3) [1] 300 signif(325.4,0) [1] 300 may not be what you expect. Sometimes it is better not to document things than try to give precise details which may get changed *and* there will be useRs who misread (and maybe even file bug reports on their misreadings). The source is the ultimate documentation. -- Brian D. Ripley, rip...@stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UKFax: +44 1865 272595 __ 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.
Re: [R] round() and negative digits
On 11-10-07 5:26 PM, Carl Witthoft wrote: Just wondering here -- I tested and found to my delight that % round(325.4,-2) [1] 300 gave me exactly what I would have expected (and wanted). Since it's not explicitly mentioned in the documentation that negative 'digits' is allowed, I just wanted to ask whether this behavior is intentional or a happy turn of events. I'm always paranoid that something not explicitly documented might disappear in future revisons. It is intentional, and one of the regression tests confirms that it's there, so it won't disappear by mistake, and would be very unlikely to disappear intentionally. Duncan Murdoch __ 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.
Re: [R] round() and negative digits
On 11-10-08 5:32 PM, Rolf Turner wrote: On 09/10/11 00:18, Duncan Murdoch wrote: On 11-10-07 5:26 PM, Carl Witthoft wrote: Just wondering here -- I tested and found to my delight that % round(325.4,-2) [1] 300 gave me exactly what I would have expected (and wanted). Since it's not explicitly mentioned in the documentation that negative 'digits' is allowed, I just wanted to ask whether this behavior is intentional or a happy turn of events. I'm always paranoid that something not explicitly documented might disappear in future revisons. It is intentional, and one of the regression tests confirms that it's there, so it won't disappear by mistake, and would be very unlikely to disappear intentionally. Uh, wouldn't it be *nice* to mention this --- not completely obvious --- capability in the help file? If we told you all of R's secrets, we'd have to kill you. Duncan Murdoch __ 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.
Re: [R] round() and negative digits
On 08-Oct-11 21:39:07, Duncan Murdoch wrote: On 11-10-08 5:32 PM, Rolf Turner wrote: On 09/10/11 00:18, Duncan Murdoch wrote: On 11-10-07 5:26 PM, Carl Witthoft wrote: Just wondering here -- I tested and found to my delight that % round(325.4,-2) [1] 300 gave me exactly what I would have expected (and wanted). Since it's not explicitly mentioned in the documentation that negative 'digits' is allowed, I just wanted to ask whether this behavior is intentional or a happy turn of events. I'm always paranoid that something not explicitly documented might disappear in future revisons. It is intentional, and one of the regression tests confirms that it's there, so it won't disappear by mistake, and would be very unlikely to disappear intentionally. Uh, wouldn't it be *nice* to mention this --- not completely obvious --- capability in the help file? If we told you all of R's secrets, we'd have to kill you. Duncan Murdoch A Fortunate remark?? That being said -- if such are your intentions, then over my dead body ... Carl Witthoft's serendipitous discovery is a nice example of how secrets can be guessed by wondering what if ... ?. So probably you don;t need to tell the secrets. Taking the negative digits to their logical extreme: round(654.321,2) # [1] 654.32 round(654.321,1) # [1] 654.3 round(654.321,0) # [1] 654 round(654.321,-1) # [1] 650 round(654.321,-2) # [1] 700 round(654.321,-3) # [1] 1000 round(654.321,-4) # [1] 0 which is what you'd logically expect (but is it what you would intuitively expect?). Ted. E-Mail: (Ted Harding) ted.hard...@wlandres.net Fax-to-email: +44 (0)870 094 0861 Date: 08-Oct-11 Time: 23:11:27 -- XFMail -- __ 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.
Re: [R] round() and negative digits
On 10/8/11 6:11 PM, (Ted Harding) wrote: Carl Witthoft's serendipitous discovery is a nice example of how secrets can be guessed by wondering what if ... ?. So probably you don;t need to tell the secrets. Taking the negative digits to their logical extreme: round(654.321,2) # [1] 654.32 round(654.321,1) # [1] 654.3 round(654.321,0) # [1] 654 round(654.321,-1) # [1] 650 round(654.321,-2) # [1] 700 round(654.321,-3) # [1] 1000 round(654.321,-4) # [1] 0 which is what you'd logically expect (but is it what you would intuitively expect?). Oh, oh, somebody's going all metaphysical on us. -- - Sent from my Cray XK6 __ 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.
