Is there an error message, and if so, what is it?
And what are the data types of 'a' and 'b' (scalar, array, ???)
In fact, if there is a way to export the problem code and display it here, that might help as well.
Also, have you read this:
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http://www.mathworks.com/help/matlab/ref/logicaloperatorselementwise.htmlI have no experience with Matlab but I have a lot of experience with computer languages. I did a bit of reading about Matlab and see possible causes for problems with using the logic operator (such as a mismatch in array/matrix dimensions), but even if I'm not able to help you, the above questions would supply the kind of information others would need to help you.