On 17/11/2016 2:19 PM, Da Zheng wrote:
Hello,

I just realized that 1^NA outputs 1 while 1.1^NA outputs NA in R v3.3.1 and
R v3.2.3.
I tried other values such as 0^NA and 2^NA, and they all output NA.
I don't understand this inconsistency here. Shouldn't 1^NA output NA as
well? Why does R handle it differently? Or is this a bug in these
particular versions of R?

Our usual interpretation of NA is "an unknown value". So 1^NA would give NA if there were multiple possible values for it depending on what number you substitute for NA, and should give the unique answer if there's only one possibility (as for example NA | TRUE gives TRUE).

As far as I can see, 1 raised to any power (even infinite ones) should give 1, so the answer looks fine to me. That's not true of any of the other bases you mention (just as NA | FALSE gives NA).

Duncan Murdoch

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