Assign NaN, get zero

Stefan van der Walt stefan at sun.ac.za
Sat Nov 11 14:36:39 CST 2006


On Sat, Nov 11, 2006 at 10:40:22AM -0800, Keith Goodman wrote:
> I accidentally wrote a unit test using int32 instead of float64 and
> ran into this problem:
> 
> >> x = M.matrix([[1, 2, 3]])
> >> x[0,1] = M.nan
> >> x
> matrix([[1, 0, 3]])   <--- Got 0 instead of NaN
> 
> But this, of course, works:
> 
> >> x = M.matrix([[1.0, 2.0, 3.0]])
> >> x[0,1] = M.nan
> >> x
> matrix([[ 1.        ,         nan,  3.        ]])
> 
> Is returning a 0 instead of NaN the expected behavior?

NaN (or inf) is a floating point number, so seeing a zero in integer
representation seems correct:

In [2]: int(N.nan)
Out[2]: 0L

Cheers
Stéfan

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