>octave:1> NaN*NA

>ans = NA

>octave:2> NA*NaN

>ans = NaN

...

>octave:5> NaN + NA

>ans = NA

>octave:6> NA + NaN

>ans = NaN

Waiting for more knowledgeable opinions, here is what I remember) caveat

emptor).

NaN is defined by IEEE standards. It has not a single binary

representations, so two NaN values may legally have different underlying

binary representations.

NA is a particular NaN representation which is used in the R language,

from which Octave copies the semantic meaning. It is commonly used in

data series to indicate a missing values (Not Available).

Examples of usage are the NaN and TSA packages, which however do not

require NA to be used, but are happy with NaN:

http://pub.ist.ac.at/~schloegl/matlab/NaN/--

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