You may have used a variable called "i" earlier in your program or session, thus overwriting the imaginary constant i with your own number. In this case, MATLAB will use your new value for i instead of treating i as sqrt(-1). Five ways to ensure that you receive a complex result are:
- Use the syntax 6i; MATLAB always interprets this as 6*sqrt(-1)
y = 6i;
- Redefine i back to sqrt(-1)
i=sqrt(-1)
y = 6*i;
- Clear your redefinition of i
clear i
y = 6*i;
- Use j instead of i (assuming you haven't used a variable called "j" earlier in you program or session)
Note: these are very good reasons for not using i & j as indexes (in FOR loops, for example)
y = 6*j;
- Use the COMPLEX function
y = complex(0, 6);
[From the MATLAB FAQ of Ancient Times]
