https://de.mathworks.com/help/matlab/apiref/mxisnan.html
mxIsNaN (C and Fortran) - Determine whether input is NaN (Not-a-Number) - MATLAB
Double-precision, floating-point number to test
nan not a number
https://mail.python.org/archives/list/numpy-discussion@python.org/thread/MMXCRPNHW6T3LOOJQMPXTHUVMUPAZSXZ/?sort=thread
Mailman 3 NaN (Not a Number) occurs in calculation of complex number for Bessel functions -...
nan not a number