[R] sum of deviations from the weighted mean
Hi all. I tried to calculate sum of deviations from the weighted mean and i didn't get what i expected - 0. Here is an example: wt - c(10,25,38,22,5) x - 6:10 wm - weighted.mean(x,wt) (x-wm)*wt [1] -18.70 -21.75 4.94 24.86 10.65 sum((x-wm)*wt) [1] -1.24345e-14 With simple mean I got 0: sum(x-mean(x)) [1] 0 Could someone explain me why we didn't get 0, with weighted mean, as it is expected? Thanks in advance Andrija [[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] sum of deviations from the weighted mean
R FAQ 7.31 I'd imagine. (Floating point arithmetic and limitations thereof) Michael On Dec 8, 2011, at 9:15 AM, andrija djurovic djandr...@gmail.com wrote: Hi all. I tried to calculate sum of deviations from the weighted mean and i didn't get what i expected - 0. Here is an example: wt - c(10,25,38,22,5) x - 6:10 wm - weighted.mean(x,wt) (x-wm)*wt [1] -18.70 -21.75 4.94 24.86 10.65 sum((x-wm)*wt) [1] -1.24345e-14 With simple mean I got 0: sum(x-mean(x)) [1] 0 Could someone explain me why we didn't get 0, with weighted mean, as it is expected? Thanks in advance Andrija [[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. __ 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] sum of deviations from the weighted mean
Thank and sorry i should check this before asking the question. Andrija On Thu, Dec 8, 2011 at 3:20 PM, R. Michael Weylandt michael.weyla...@gmail.com michael.weyla...@gmail.com wrote: R FAQ 7.31 I'd imagine. (Floating point arithmetic and limitations thereof) Michael On Dec 8, 2011, at 9:15 AM, andrija djurovic djandr...@gmail.com wrote: Hi all. I tried to calculate sum of deviations from the weighted mean and i didn't get what i expected - 0. Here is an example: wt - c(10,25,38,22,5) x - 6:10 wm - weighted.mean(x,wt) (x-wm)*wt [1] -18.70 -21.75 4.94 24.86 10.65 sum((x-wm)*wt) [1] -1.24345e-14 With simple mean I got 0: sum(x-mean(x)) [1] 0 Could someone explain me why we didn't get 0, with weighted mean, as it is expected? Thanks in advance Andrija [[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. [[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.
