Section: Inspection Functions
y = isnan(x)
The result is a logical array of the same size as x,
which is true if x is not-a-number, and false otherwise.
Note that for complex data types that
the result is true if either the real or imaginary parts
are NaNs.
nan:
--> a = [1.2 3.4 nan 5]
a = 
    1.2000    3.4000 NaN    5.0000 
--> isnan(a)
ans = 
 0 0 1 0