Jannis,
Not strange. Try with numbers that can be exactly represented in binary
(that's what computers use), e.g.,
a<-seq(5,70,by=5)
b<-15
a==b
or fractions,
a<-seq(1/32,14/32,by=1/32)
b<-3/32
a==b
Most decimal fractions cannot be represented exactly although a bit of
magic will display them as if they are.
A little digging into the r-help archives will find further explanation.
Clint
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On Mon, 20 May 2013, Jannis wrote:
Dear R users,
I ran into the strange situation where a number does not seem to equal its
value. Try this:
a <- seq(0.05,0.7,0.05)[3]
b <- 0.15
a == b
Should this not be TRUE? a-b yields a very small number (and not 0) so this
most probably is a numerical error, but why does seq create such numbers?
Thanks a lot
Jannis
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