why is 1+ nan*1i = NaN + NaNi ?

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Patrick Mboma
Patrick Mboma 2015-11-27
评论： Patrick Mboma 2015-11-28
Dear all,
I am trying to figure out how to store some information using complex numbers and retrieving that information later on.
For an operation like
1+nan*1i,
I would like to be able to retrieve "1" by doing
real(1+nan*1i)
and retrieve "nan" by doing
imag(1+nan*1i).
The first case does not work because matlab stores 1+ nan*1i as NaN + NaNi. Is there any workaround to this?
Thanks

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采纳的回答

the cyclist
the cyclist 2015-11-27
I don't envision any workaround that would specifically make NaNs work. Speaking mathematically very loosely, the NaN in your original expression could be a "complex NaN", such that the NaN-ness leaks over to the real part.
I can imagine, without deep thinking, a couple workarounds, that are annoying in their own way, but might work in your particular situation.
  • Use another matrix dimension to keep real and imaginary parts separate
  • Define your own complex number object, that has the properties you outline above.

更多回答（1 个）

Walter Roberson
Walter Roberson 2015-11-27
A = complex(1,nan)
real(A), imag(A)
B = A
However if you were to do
2*A
then you would get complex(NaN, NaN). You can use complex() to force unusual structures such as complex(5,0) but any arithmetic on it is going to demote it to complex(NaN, NaN)
  1 个评论
Patrick Mboma
Patrick Mboma 2015-11-28
Hi Walter,
Thanks for the reply. I did not know about the complex function. Thanks also for making me aware of it.
Your solution will surely work if I have a scalar. But if I start stacking items in a vector, I am not sure what the results will be. For now I think I will use the safe option of just creating another dimension to keep the numbers separate.

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