Imag, real function error

when I try to use the imag or real functions I get an error saying 'Subscript indices must either be real positive integers or logicals.' I don't get this when I use the isreal or abs functions. Why is this?

[James Tursa]

Please post your code that generates this error.

[Sean Pitre]

Its a two line test code. Like,

X=2+3i
Y=real(x) or imag(x).

Even if I do it directly like Real(2+3i) I get the error

[James Tursa]

Try clearing all variables first, and then re-try your code to confirm that it is a variable naming issue or not.

Answer 1

[James Tursa]

It could be that you have inadvertently created variables with the name "real" or "imag" that are shadowing the functions real and/or imag.

Answer 2

[Star Strider]

My guess is that you used ‘imag’ and ‘real’ as variables somewhere earlier in your code. The solution is to find those variables and rename them. (The builtin (link) function can shed light on this.)

Example —

imag = 42;
x = 1 + 2*j;

A1 = builtin('imag', x)
A2 = imag(x)

yields:

A1 =
     2.0000e+000

For ‘A2’:

Subscript indices must either be real positive integers or logicals.

Error in FileName (line #####)
A2 = imag(x)

[Sean Pitre]

The code I have is two lines long. I just declare a variable x as some complex number then try to get the real part of that number. I'll check again to see if maybe I missed something. My code is just x = 2 + 3i y = real(x)

[James Tursa]

What does this show?

which real
which imag

[Star Strider]

The which function can be helpful.

Note all the results from:

which real -all

If the first result is:

real is a variable.

you’ve found the problem.