MATLAB Central Newsreader - imag and real don't work

imag and real don't work

Sandra — Thu, 24 Jul 2008 11:04:04 -0400

I am sure this must be a simple thing, but it is doing my
head in!!! imag and real don't work for me see below:

>> real(0.0116 + 0.3333i)
??? Subscript indices must either be real positive integers
or logicals.

>> real(2+3*i)
??? Subscript indices must either be real positive integers
or logicals.

>> imag(2+3*i)
??? Subscript indices must either be real positive integers
or logicals.

the last two are from the matlab example! what am I doing wrong?

any advice appreciated,
sandra

Re: imag and real don't work

Dave Brackett — Thu, 24 Jul 2008 11:08:03 -0400

"Sandra " <smh31.nospam@sussex.ac.uk> wrote in message
<g69nj3$9he$1@fred.mathworks.com>...
> I am sure this must be a simple thing, but it is doing my
> head in!!! imag and real don't work for me see below:
>
> >> real(0.0116 + 0.3333i)
> ??? Subscript indices must either be real positive integers
> or logicals.
>
> >> real(2+3*i)
> ??? Subscript indices must either be real positive integers
> or logicals.
>
> >> imag(2+3*i)
> ??? Subscript indices must either be real positive integers
> or logicals.
>
>
> the last two are from the matlab example! what am I doing
wrong?

Check that you haven't assigned anything to i. i and j
should be reserved for complex numbers. type 'clear i' in
command window and then try again.
dave

Re: imag and real don't work

John D'Errico — Thu, 24 Jul 2008 11:13:08 -0400

"Sandra " <smh31.nospam@sussex.ac.uk> wrote in message
<g69nj3$9he$1@fred.mathworks.com>...
> I am sure this must be a simple thing, but it is doing my
> head in!!! imag and real don't work for me see below:
>
> >> real(0.0116 + 0.3333i)
> ??? Subscript indices must either be real positive integers
> or logicals.
>
> >> real(2+3*i)
> ??? Subscript indices must either be real positive integers
> or logicals.
>
> >> imag(2+3*i)
> ??? Subscript indices must either be real positive integers
> or logicals.
>
>
> the last two are from the matlab example! what am I doing wrong?
>
> any advice appreciated,
> sandra

Every single new user does this. They create
a variable with the name of a function they
will later use.

Have you created variables named imag and
real? What should Matlab do when it sees
variables with that name, but you try to use
the functions of the same names?

Just for kicks, now create variables named
quit and exit, as well as clear. Make your life
interesting. ;-)

John

Re: imag and real don't work

Bruno Luong — Thu, 24 Jul 2008 11:15:09 -0400

Rather check real and imag.

clear real imag % clear variables
which real
which imag

If it does not return built-in functions then you have a
files that overwrite MATLAB factory functions.

Bruno

Re: imag and real don't work

Matt Fig — Thu, 24 Jul 2008 12:37:03 -0400

real = 1:4;
real(3+2*i)
??? Subscript indices must either be real positive integers
or logicals.

clear real
real(3+2*i)

ans =

3