Re: [R] Floating point imprecision in sum() under R-2.3.1?

From: Brahm, David <David.Brahm_at_geodecapital.com>
Date: Sat 19 Aug 2006 - 06:04:53 EST


I was concerned by this result (new in R-2.3.1): R> x <- c(721.077, 592.291, 372.208, 381.182) R> sum(x) - 2066.758

   [1] 4.547474e-13

But after Roger Peng's <rdpeng@gmail.com> insightful comment that the relative difference (sum(x)/2066.758 - 1) is exactly what is expected, I'm convinced that sum() is indeed really being "more accurate" than it was in 2.2.1, i.e. accurately preserving the numerical imprecision of the original inputs. Sorry for the distraction...


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