Hi, When I used x <- c(10,10,10,10,5,5,5,5) sum(x) x <- x - .Last.value/8 the result was zero, as I expected. However, when I used x <- rnorm(101,0,10) sum(x) x <- x - .Last.value/101 sum(x) I did not get zero, but -2.664535e-15. OK, that's fairly close to zero, but I tried to improve the figure. Each time I repeated the last two commands, the sum got closer to zero. The series seemed to converge on -1.30e-15, so changed the 101 to 50, then to 20, and then to 10. I had sum(x) down to -5.551115e-17 before I quit.
If R can store values of x which sum to -5.551115e-17, then why can't I get that value on the first try? Is this a bug or just rounding error? Jim Frederick ______________________________________________ [email protected] 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.
