On 9/30/2009 2:50 PM, Michael Knudsen wrote:
On Wed, Sep 30, 2009 at 8:44 PM, Duncan Murdoch <murd...@stats.uwo.ca> wrote:
Why? You asked for an increment of 1 in the second case (which is exactly
represented in R), then divided by 10, so you'll get the same as 0.3 gives
you. In the seq() case you asked for an increment of a number close to but
not equal to 1/10 (because 1/10 is not exactly representable in R), so you
got something different.
Well, the problem is that I don't know how seq is implemented. I just
assumed that it wouldn't behave like this.
It doesn't really matter how it is implemented: if you ask to start at
0.1 and increment by 0.1, you should expect the result to be the same as
0.1
0.1+0.1
0.1+0.1+0.1
etc.
and I think it is. The problem is that 0.1+0.1+0.1 is not the same as
0.3, due to rounding. Neither 0.1 nor 0.3 can be represented exactly in
the standard IEEE floating point formats that R uses.
Duncan Murdoch
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