How can I convert back the _FillValue elements from zero to NaN

I have A matrix which contains NaN as a _FillValues and inf values. I wanted to convert the inf values to zero by:

   A(~isfinite(A)) = 0.

This function changed the NaN values to zero. I tried get back NaN values by the following functions:

   A(isnan(A)) = nan

   A(A == attval3) = nan

 But the NaN values remain zero. How can I convert back the _FillValue elements to NaN?

Answer 1

[Guillaume]

Well, once you've replaced the NaNs in A by 0, isnan(A) is never going to find any NaN. Unless you've kept a copy of the original A around there's no way to find out where they were.

To replace just the Inf and not the NaN in the unmodified, original A, use isinf:

A(isinf(A)) = 0; %or A(~isnan(A) & ~isfinite(A))

[Szabó-Takács Beáta]

Thank you Guillaume very much for help! It works.