understanding an if statement

What does this mean ?

Can you please explain with an example ?

if not(max(c))c

Thanks

Answer 1

[DGM]

This isn't very clear usage and looks like invalid syntax at first glance. It would help to know what the surrounding code looks like and what c is (its size and type).

What looks like invalid syntax (an implicit multiplication with the trailing instance of c) is actually parsed like this:

c = [0 1 2 3]; % let's assume c is a numeric or logical vector

if not(max(c)) % true if largest value of c is <= 0
    c % this is treated as a separate expression on another line
    disp('tested true')
else
    disp('tested false')
end

tested false

The condition will only test true if all elements of c are less than or equal to zero. You could do the same thing like so:

if all(c<=0) % true if c contains no positive nonzero values
    % ...
end

Given the way this is written, it's not clear that this is the actual intent.

If the intent is for the test to be true only when all elements of c are equal to zero, you could do that instead:

if all(c==0) % true if c contains no nonzero elements
    % ...
end

or

if nnz(c) == 0 % true if c contains no nonzero elements
    % ...
end

or

if ~any(c) % true if c contains no nonzero elements
    % ...
end