# [R] = vs. ==?

(Ted Harding) Ted.Harding at manchester.ac.uk
Wed Apr 16 16:38:28 CEST 2008

```On 16-Apr-08 11:13:40, Alberto Monteiro wrote:
>
> Ted Harding wrote:
>>
>> One is that "NA" is not a value. Its logical status is,
>> in effect, "value not known". Therefore, when 'y' is "NA",
>>  "x==y" cannot have a definite resolution, since it is
>> possible for the unkown value of 'y' to be equal to the
>> value of 'x'; and equally possible that it may not be.
>> Hence the value of "x==y" is itself "NA". Similarly
>> the value of "x==y" is "NA" when both of 'x' and 'y'
>> are "NA". The function to use for testing whether (say)
>> 'x' is "NA" is is.na(x).
>>
> Just as an off-topic tangent, I found it quite interesting
> that real-world language Aymara (see ...
> http://en.wikipedia.org/wiki/Aymara_language
> ...) uses this three value logic system (I think the
> computer jargon is "trollean logic").
>
> Alberto Monteiro

Equally interesting (and equally OT) to us as people concerned
with information and evidence is that some real-world langauges
have a specific provision for expressing the evidential status
of the information they express. It seems that this has only
relatively recently been formalised by linguists under the

For example, Turkish has the suffix [transcribed] mish/mush
to indicate whether what is stated is known directly or
indirectly.

Thus, at the Department Meeting we are all waiting for
X to turn up, so that we can start. Finally, I phone his
home. His wife answers. I ask about X. She says "Geliyor"
[He is coming]. She knows this because she has just seen
him leave the house.

I turn round to report this: I say "Geliyormush", because
I don't know it. What I do know is that I have been told it.

For more: http://en.wikipedia.org/wiki/Evidentiality

In the same vein, you might tell me what I regard as a
tall tale. I could respond "Mush!", with meaning on the
lines (in escalating order)of: "So you say!", "Pull the
other one!", "Come off it!", ...

Best wishes to all,
Ted.

--------------------------------------------------------------------
E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 16-Apr-08                                       Time: 15:38:24
------------------------------ XFMail ------------------------------

```