On Tue, Aug 2, 2016 at 1:02 PM, Chris Barker <chris.barker@noaa.gov> wrote:
I don't think IEE754 says anything about a "clip" function, but a NaN is neither greater than, less than, nor equal to any value -- so when you ask if, for example, for the input value if it is less than or equal to NaN, but NaN if NaN is great then the input, there is no answer -- the spirit of IEEE NaN handling leads to NaN being the only correct result.
Note that I'm pretty sure that min() and max() are wrong here, too.
Builtin max is wrong
nan = float('nan') max(nan, 1) nan max(1, nan) 1
but numpy's maximum gets it right:
numpy.maximum(nan, 1) nan numpy.maximum(1, nan) nan
And here is how numpy defines clip:
numpy.clip(nan, 1, 2) nan numpy.clip(1, 1, nan) 1.0 numpy.clip(1, nan, nan) 1.0
I am not sure I like the last two results.