finding the index of NaN

Consider the array A:

A = [10 30 NaN 30]

When I use the expressin below, a new logical array is created with columns with a value of 1 for elements of A equal to 30:

A == 30
>> 0 1 0 1

But why does not the expression below works and it outputs with all columns with a value of 0, although the third element should be 1 as it is a NaN:

A == NaN
>> 0 0 0 0

Answer 1

[MJFcoNaN]

You may use "isnan"

A = [10 30 NaN 30]

A = 1×4

10 30 NaN 30

isnan(A)

ans = 1×4 logical array
   0   0   1   0

PS: There is a tip from help document

"NaN values are not equal to each other. As a result, comparison operations involving NaN return false, except for the not equal operator ~=. For example, NaN == NaN returns logical 0 (false) but NaN ~= NaN returns logical 1 (true)."