[R] Bug in "seq" (or a "feature") ?

[Erik Iverson]

General floating point arithmetic issue here:

See FAQ 7.31

http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f



-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Tal Galili
Sent: Monday, August 10, 2009 4:14 PM
To: r-help at r-project.org
Subject: [R] Bug in "seq" (or a "feature") ?

(I use R 2.9.1 with win XP)

If I run this code:
seq(-0.1,.9, by = .05)[seq(-0.1,.9, by = .05) <= 0.5]
I get this output:
[1] -0.10 -0.05 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
Why is 0.50 not in the results ?
(It seems that it gives a slightly bigger number then 0.5 but I don't
understand why it does that)


Where as if I try:
seq(-0.1,.9, by = .05)[seq(-0.1,.9, by = .05) <= 0.4]
and get:
[1] -0.10 -0.05 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40
Then 0.40 WILL be in the results.

Thanks,Tal




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