[R] bug?

[Uwe Ligges]

Marc Vandemeulebroecke wrote:

> Dear R programmers,
> 
> is there a sensible explanation for the following behaviour? The second
> command seems not to be interpreted correctly.
> 
> 
>>seq(0.6, 0.9, by=0.1) == 0.8
> 
> [1] FALSE FALSE  TRUE FALSE
> 
>>seq(0.7, 0.9, by=0.1) == 0.8
> 
> [1] FALSE FALSE FALSE
> 
>>c(0.7, 0.8, 0.9) == 0.8
> 
> [1] FALSE  TRUE FALSE
> 
>>seq(0.9, 0.7, by=-0.1) == 0.8
> 
> [1] FALSE  TRUE FALSE
> 
> I am running R version 1.7.1 on XP and NT.
> 
> Thanks,
> Marc
> 
> --
> 
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It is correct, just an instability of the representation of that 
floating point number, because (regularly) floating point numbers cannot 
be represented exactly.

Uwe Ligges