NaN is designed to propagate through all calculations, infecting them like a virus, so if somewhere in your deep, complex calculations you hit upon a NaN, you don't bubble out a seemingly sensible answer. Otherwise by identity NaN/NaN should equal 1, along with all the other consequences like (NaN/NaN)==1, (NaN*1)==NaN, etc.

2013年12月2日 · No, as I said in the original question, nans aren't unique objects. Look at the above transcript: the two nans have different ids and nans[0] is nans[1] is False. nan in [nan] is True because it's basically any(x is nan or x == nan for x in [nan]). x is nan is True so it doesn't matter that x == nan is False.

2013年7月25日 · NaN preserving and NA preserving work "equivalently" in R, so if you agree that NA^0 should give 1, NaN^0 |-> 1 is a consequence. Indeed (as others said) you should really read R's help pages and not C or IEEE standards, to answer …

2013年7月24日 · Different operating systems and programming languages may have different string representations of NaN: nan NaN NaN% NAN NaNQ NaNS qNaN sNaN 1.#SNAN 1.#QNAN -1.#IND I think having all three is just a convenience. They are the same. >>> np.nan nan >>> np.NaN nan >>> np.NAN nan >>>

2018年3月29日 · Type Result Null +0 Undefined NaN And NaN + anything is NaN. This might make some sense from the language perspective: null means an explicit empty value whereas undefined implies an unknown value. In some way - zero is the "number empty value" since it is neutral to addition.

2009年12月18日 · NAN may or may not be defined, and "is defined if and only if the implementation supports quiet NaNs for the float type. It expands to a constant expression of type float representing a quiet NaN." Note that if you're comparing floating point values, and do: a = NAN; even then, a == NAN; is false. One way to check for NaN would be:

2023年7月13日 · float('nan') represents NaN (not a number). But how do I check for it?

2015年1月20日 · Present in the legacy GAC, c:\windows\assembly, it also has the 10.1.0.0 version. There is a DLL Hell story here, the 10.1.0.0 version was the one used in VS2010. It had the bug, not properly checking for Double.NaN. Microsoft made a mistake, they fixed 10.1.0.0 but did not change the version number.

2009年2月21日 · nan results from the operation 0.f/0.f, or 0.0/0.0. nan is a terrible nemesis to the stability of your code that must be detected and prevented very carefully 1. The properties of nan that are different from normal numbers: nan is toxic, (5*nan=nan) nan is not equal to anything, not even itself (nan!= nan) nan not greater than anything (nan!> 0)

2016年5月31日 · Generally there are two steps - substitute all not NAN values and then substitute all NAN values. dataframe.where(~dataframe.notna(), 1) - this line will replace all not nan values to 1. dataframe.fillna(0) - this line will replace all NANs to 0