Hi, I just observed a strange behavior in R. The rnorm function does not give me the numbers with a given length. I think it is somehow related to the internal representation of double-type numbers but I am not sure if this is supposed to happen. Below is a reproducible example
``` ## Create a list, we will only take the forth value, which is 0.6 nList <- seq(0,1,0.2) n <- nList[4] n # [1] 0.6 length(rnorm(1000*n)) # [1] 600 length(rnorm(1000-1000*n)) # [1] 399 <--- What happened here? length(rnorm(1000-1000*0.6)) # [1] 400 1000-1000*n # [1] 400 <- this looks good to me... 1000-1000*0.6 # [1] 400 identical(n, 0.6) # [1] FALSE .Internal(inspect(n)) # @0x00000217c75d79d0 14 REALSXP g0c1 [REF(1)] (len=1, tl=0) 0.6 .Internal(inspect(0.6)) # @0x00000217c791e0c8 14 REALSXP g0c1 [REF(2)] (len=1, tl=0) 0.6 ``` As you can see, length(rnorm(1000-1000*n)) does not really give me the result I want. This is somewhat surprising because it is hard to imagine that a manually-typed 0.6 can behave differently than 0.6 from a sequence. Furthermore, 0.6 is the only problematic number from `nList`. The rest numbers work fine. I can guess it is due to the rounding mechanism, but I think this should be treated as a bug: if the print function can show the result of 1000-1000*n correctly, it will be strange that rnorm behaves differently. Below is my session info R version 4.3.0 (2023-04-21 ucrt) Platform: x86_64-w64-mingw32/x64 (64-bit) Running under: Windows 10 x64 (build 19045) Matrix products: default locale: [1] LC_COLLATE=English_United States.utf8 [2] LC_CTYPE=English_United States.utf8 [3] LC_MONETARY=English_United States.utf8 [4] LC_NUMERIC=C [5] LC_TIME=English_United States.utf8 time zone: America/Chicago tzcode source: internal ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
