Re: NaN and missing values

[Joao Cardoso]

"John W. Eaton" wrote:
> 
> On 23-Sep-1999, heberf <address@hidden> wrote:
> 
> | Yes, that would do it.  We would also need a load command which
> | would interpret two data seperators (like TAB or commas for csv
> | files) as a missing value.  Another issue is how will the matrix X
> | appear when you type X at the prompt.  My recommendation would be
> | that a missing value gets displayed as a .  on the screen.  This
> | seems to be more or less standard.
> 
> In text data files, missing data could be represented as a single
> `.'.  It seems reasonable to use that for display too.

At this point of the discussion it seems clear that many of us and most
stat packages use NaNs to code missing values.
It is thus important to consider the question on how to save/load such
data. My OS support NaNs on binary files, so I can save/load them from
within Octave without problem. The situation is different for text
files, as `scanf' and family don't *read* NaNs.

Some of you might remember a patch to libstdc++ that I announced some
months ago. That question has raised many discussions on the libstdc++
mailing list, as it seems that *no* standard address the question of
reading a NaN/Inf (a text string) using the familiar `%f' format
character. And libstdc++ *wants* to conform with standards, although
somebody suggest implementing the capability as an extension.

Please take this issue in consideration when discussing NaNs/Infs.

Has someone a place on a standard committee? :-)

Joao


> 
> jwe
> 
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Joao Cardoso                |   e-mail: address@hidden
INESC, R. Jose Falcao 110   |   tel:    + 351 2 2094322
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