On Wed, Mar 21, 2012 at 5:21 PM, Mike Williamson <this.is....@gmail.com> wrote: > Thanks Sarah, All, > > I guess I never thought of a negative sign as an "operation", but > knowing that it is considered an operation explains everything nicely. > Somewhere in it's underbelly, I suppose -4 is represented as "0 - 4"?
Sheesh! And why do you suppose that?! Read up on floating point arithmetic to find out how it is done. -- Bert > Either way, I'm glad it is consistent & accurate, so that I didn't find > myself in another pickle like "weak" typing and attempts to use time /date > classes in 'R' have brought me. > > Thanks! > Mike > > > --- > [The theory of gravity] is to me so great an absurdity that I believe no > Man who has in philosophical matters a competent faculty of thinking can > ever fall into it. -- Isaac Newton > > > > On Wed, Mar 21, 2012 at 4:37 PM, Rolf Turner <rolf.tur...@xtra.co.nz> wrote: > >> On 22/03/12 12:17, Sarah Goslee wrote: >> >>> It's order of operations, and a good reason to always use >>> parentheses: which is evaluated first, the unary minus or >>> the raising-to-powers? >>> >>> (-4)^0.5 >>> -(4^0.5) >>> >>> sqrt(-4) >>> -sqrt(4) >>> >> >> If the OP *really* wants the square root of -4 he could do >> sqrt(-4+0i) or (-4+0i)^0.5 (and get 0+2i in either case). >> >> cheers, >> >> Rolf Turner >> > > [[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. -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm ______________________________________________ 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.
