On Fri, 11 Feb 2005 [EMAIL PROTECTED] wrote:
Full_Name: Chris Spencer Version: 2.0.1 OS: Linux Submission from: (NULL) (163.1.211.93)
Dear R team,
I realise that the following is a bit unsafe (the combination of doubles and integers), however I wondered whether the following behaviour is expected:
#Test R test <- vector(length=100000); for(i in 1:100000){temp = i/1000; test[i] = (i == temp*1000);} table(test);test FALSE TRUE 1472 98528
Certainly. You might even expect worse behaviour than that.
temp can be exactly represented in double precision only when i is a multiple of 125. Depending on exactly how the computations are done and how many extra guard digits are carried you could get FALSE for nearly all i not a multiple of 125. The fact that you get TRUE 98% of the time is better accuracy than you should expect.
-thomas
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