8000 np.nan has negative sign, should be positive. (Trac #920) · Issue #1518 · numpy/numpy · GitHub
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np.nan has negative sign, should be positive. (Trac #920) #1518

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thouis opened this issue Oct 19, 2012 · 4 comments
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np.nan has negative sign, should be positive. (Trac #920) #1518

thouis opened this issue Oct 19, 2012 · 4 comments
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00 - Bug component: Other
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1.3.0

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@thouis
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thouis commented Oct 19, 2012

Original ticket http://projects.scipy.org/numpy/ticket/920 on 2008-10-02 by @charris, assigned to unknown.

On my reverse endian machine

In [3]: array([np.nan]).tostring()
Out[3]: '\x00\x00\x00\x00\x00\x00\xf8\xff'
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thouis commented Oct 19, 2012

@cournape wrote on 2009-03-09

Chuck, what's the rationale for having a positive nan ?

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thouis commented Oct 19, 2012

@charris wrote on 2009-03-09

Hi David,

I don't think it matters much, the ieee spec says the sign of nan is undefined. This turned up when I was working on the signbit functions and it just seemed the right thing to do. But go ahead and close the ticket, anything that depends on the sign of a nan is probably an error.

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thouis commented Oct 19, 2012

@charris wrote on 2009-03-10

However, the gcc NAN macro give a positive nan and the sign of nans is accessible through the signbit ufunc. Copysign also returns the signbit for nans. So it just seems a little nicer to make it positive. The easy way is to use copysign on the computed nan:

mynan = copysign(mynan, 1.0);

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thouis commented Oct 19, 2012

@cournape wrote on 2009-03-11

Fixed in r6634

@thouis thouis closed this as completed Oct 19, 2012
@thouis thouis mentioned this issue Oct 23, 2012
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