In this case, Matlab would evaluate the logical operators from left to right. See Operator Precedence for instances when this would not be the case.

That would mean that ~(5>4) | (1>10) would first evaluate the left half of the OR:

~(5>4) --> ~(1) --> 0

Then continuing...

0 | (1>10) --> 0 | 0 --> 0

Unlike in natural language, you have to write out a complete comparison on both sides of the boolean operators, that's how it works. So you can't leave out num in the second part like you did.

Matlab complains about ~= because it didn't expect that symbol right after the & operator.

Try this instead:

B = num > 0 & num ~= 1

Solution

Use the following syntax:

res = ~any(~isnan(X(:)));

if res==true it means that that the matrix contains only nan values.

Example

X = nan(3,3)
~any(~isnan(X(:)))

X(1,2) = 0;
~any(~isnan(X(:)))

Results

ans = 1
ans = 0