numeric not equal its value

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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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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