I have no problem with -2^2 = 4 if we have consistency. R -2^2 = -4 Spreadsheets -2^2 = 4
Which is "TRUE"? (For some nebulous value of "TRUE") For a relatively unsophisticated user this does not bode well if he or see is transferring work from one application to another. John Kane Kingston ON Canada > -----Original Message----- > From: erich.neuwi...@univie.ac.at > Sent: Fri, 18 Sep 2015 18:06:23 +0200 > To: jrkrid...@inbox.com > Subject: Re: [R] Spreadsheet math problem (exponentiation) > > Methinks that any math teaching should make learners aware of the fact > that > math conventions are not laws of nature, and that ambiguous expressions > may > produce different values in different systems. > > I think -2^2=4 is perfectly reasonable. > > In my experience, most people after high school math do not know that > binary - und unary - are very different operations. > And that is the fault of the current way of teaching math! > > > >> On Sep 18, 2015, at 18:00, John Kane <jrkrid...@inbox.com> wrote: >> >> A very good point re RExcel for sophisticated users. The majority of >> spreadsheet users, will never have heard of RExcel (or R for that >> matter) and very likely will no have the sophistication of knowing that >> they need to use brackets. Plus RExcel is not available in flavours >> for Apache OpenOffice or gnumeric as far as I am aware. >> >> If one actually learned the formal mathematical order of operations and >> still remembers them the expectation is that -2^2 will return -2. In a >> 20 sheet spreadsheet the error is likely to go completely undetected and >> may or may not have significant effect on final results. >> >> I, recently, was reading an education blog where the author was >> bemoaning the fact that shiny new math teachers were teaching that -2^2 >> = 4. Presumably they are putting their faith in Excel, etc., rather than >> the actual math conventions. >> >> John Kane >> Kingston ON Canada >> >> >>> -----Original Message----- >>> From: erich.neuwi...@univie.ac.at >>> Sent: Fri, 18 Sep 2015 17:13:44 +0200 >>> To: r-help@r-project.org >>> Subject: Re: [R] Spreadsheet math problem (exponentiation) >>> >>> Let me add a little bit here: >>> >>> When using math formulas, one should know about the parsing rules form >>> complex expression >>> which do not have all the necessary parenthesis. >>> >>> Different systems do have different parings rules. >>> In the case of a^b^c, the expression is ambiguus because >>> (as mentioned in a previous mail) in general >>> (a^b)^c != a^(b^c) >>> To avoid unintended consequences, just us parentheses and you will get >>> the right result. >>> in the case of -a^b >>> The question is the order of precedence of unary - and binary ^. >>> >>> In Excel, -2^2=4, but 0-2^2=-4 >>> >>> Reason: For Excel, unary - is stronger than the power operator, but >>> binary minus is weaker. >>> >>> My feeling is that too many people are bashing spreadsheets for the >>> wrong >>> reason. >>> Spreadsheets ca do things R cannot do: Automatic recalculation when >>> input >>> changes, >>> and visual point and click modelling of dependencies. >>> The calculation engine of Excel admittedly has some weak points. >>> >>> That is the reason why I wrote RExcel which gives you all the >>> advantages >>> of the spreadsheet interface >>> and allows you to use the R calculation within this interface whenever >>> needed. >> >> ____________________________________________________________ >> Send any screenshot to your friends in seconds... >> Works in all emails, instant messengers, blogs, forums and social >> networks. >> TRY IM TOOLPACK at http://www.imtoolpack.com/default.aspx?rc=if2 for >> FREE >> >> ____________________________________________________________ Can't remember your password? Do you need a strong and secure password? Use Password manager! It stores your passwords & protects your account. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
