Imaginary number to a power

I've been getting inconsistent results from a simple piece of code: 'i^3'. I expect this to yield 0,-1.0i. I get this result some times but many times I get -1.0 instead. Prior to this I enter 'i=sqrt(-1)' to ensure i is properly defined. I've tried 'clear all', 'clear functions', and exiting MATLAB and getting back in but still get inconsistent results.

Any idea why this happens? I'm running R2008b (7.7.0.471). Thanks...

Answer 1

[Matt Fig]

No problem here:

clear i
correct_answer = i^3 % Verify this first!

for ii = 1:100000, 
    if ~isequal(i^3,correct_answer)
        disp('Uh-oh')
        break
    end
 end

Are you sure you haven't been using i as a loop variable?