I work in matlab a lot and have had this error creep up several times. It's very annoying, to say the least.
The better fix - which I mentioned as well - is to use `2+3i` instead of `2+3*i`. The former will always use sqrt(-1).
I agree. I think I picked up this syntax from Python. My response was intended as tongue-in-cheek answer since Matlab allows both i and j as the complex number. I mainly see this when editing or modifying scripts written by others in my lab and have to pinpoint their counter usage.