Why is 6*i not a complex number in my program?

I though i was for imaginary in MATLAB.

Answer 1

[Doug Hull]

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]

Answer 2

[Anish]

Looks like you might have a variable defined named "i" which is a real. If this is the case, then the "definition" of "i" as imaginary unit is overridden. For example:

i = 6;

disp(6*i)

Output:

36

See:

http://www.mathworks.com/help/techdoc/ref/i.html