[PYTHON MATRIX-SIG] Handling null data points

[Jim Fulton]

Konrad Hinsen wrote:
> 
> > NaN sounds interesting - at the moment I just use 1e20. This works fine
> > for me as I only have to handle vectors of floats but it would be nice
> > to have a solution that would be applicable to other data types.
> 
> NaN is part of the IEEE float format specification, so it wouldn't be
> available for anything but floats. There's also infinity (positive
> and negative) as a special value. But it is somewhat risky to use
> them as "no data" identifiers because some functions return them
> as error indicators (e.g. sqrt(-1) is NaN). You would never know
> whether a certain data item is unknown or the result of an undefined
> operation.

In some systems I've worked with that supported missing values, 
calling a function with a value outside its range yielded a 
missing result.  So I think the example you give is reasonable. :-)
This is a debatable point though.   

-- 
Jim Fulton         Digital Creations
jim@digicool.com   540.371.6909
## Python is my favorite language ##
##     http://www.python.org/     ##

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