> %/% which, BTW, > violated the sacred rule that for all a, and non-zero b: > > a = b * (a %/% b) + a %% b > > Namely, that Inf %/% n is not Inf, but NaN.
But the other sacred rule is that a%%b is >=0 and <b. By the way, you will run into problems with %% long before Inf. E.g., > (1 + 2^53) %% 2 # 1 if you had infinite precision [1] 0 > (2 + 2^53) %% 2 [1] 0 Warning message: probable complete loss of accuracy in modulus Bill Dunlap TIBCO Software wdunlap tibco.com On Wed, Mar 11, 2015 at 4:25 AM, ALBERTO VIEIRA FERREIRA MONTEIRO < albm...@centroin.com.br> wrote: > I've just found an annoyance with the behaviour of %/% which, BTW, > violated the sacred rule that for all a, and non-zero b: > > a = b * (a %/% b) + a %% b > > Namely, that Inf %/% n is not Inf, but NaN. > > Why is this so? It's an annoyance, because in expressions like: > > big.vector.1[a, b, c] <- big.vector.2[a, b, c] %/% n > > we must treat Inf and -Inf as exceptions, when a simple division does > not have these exceptions > > BTW, I treated this exception the way Grace Hopper would be proud of, > namely, > "it's easier to ask forgiveness than it is to get permission", but at > the cost of memory: > > big.vector.1 <- big.vector.2 > big.vector.1[a, b, c] <- big.vector.2[a, b, c] %/% n > tst <- is.nan(big.vector.1) > if (any(tst)) big.vector.1[tst] <- big.vector.2 > > Alberto Monteiro > > ______________________________________________ > 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. > [[alternative HTML version deleted]] ______________________________________________ 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.
