[R] understanding all.equal() output: "Mean relative difference"
landronimirc at gmail.com
Thu Nov 24 13:44:45 CET 2011
How should one parse all.equal() output? I'm specifically referring to
the 'mean relative difference' messages. For example,
> all.equal(pi, 355/113)
 "Mean relative difference: 8.491368e-08"
But I'm not sure how to understand these messages. When they're close
to 0 (or 1xe-16), then it's intuitive. But when they're big,
> all.equal(1, 4)
 "Mean relative difference: 3"
> all.equal(2, 4)
 "Mean relative difference: 1"
> all.equal(3, 4)
 "Mean relative difference: 0.3333333"
the messages start making much less sense. I tried Wikipedia , but
the description is cryptic, as is the help page. Also, Fox and
Weisberg (2011) don't explain this particular message.
Do you know how to read?
Do you know how to write?
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