"roots" function not working

Hi,

I need to use the roots function to find the roots of a polynomial. I copied the text from the example @ the MathWorks.com entry for this function:

p = [1 -6 -72 -27];
r = roots(p);

However, r does not return, and the following error appears:

??? Subscript indices must either be real positive integers or logicals.

I cannot believe that Matlab cannot execute this simple code that is an official example. Does someone have any insight as to what the problem may be?

Answer 1

[Matt Fig]

You have a variable named roots. Do this :

clear roots
p = [1 -6 -72 -27];
r = roots(p);

Don't name variables after built-in MATLAB functions. (And especially don't blame MATLAB for your silly mistakes ;-))

[Jan]

@Kyle: For checking: "which roots -all"

[Kyle]

This was my problem. Oops. Thank you very much.

[Anowarul Azim Evan]

rt=[1 1 1 1 1]; % all roots are 1 like (x-1)*(x-1)*(x-1)*(x-1)*(x-1)
p=poly(rt)  % right-most is the constant value then x coefficient, then x^2 and so on...
roots(p)
%% roots
   1.0008 + 0.0006i
   1.0008 - 0.0006i
   0.9997 + 0.0009i
   0.9997 - 0.0009i
   0.9990 + 0.0000i

   %% Is it any bug? I was supposed to get 5 ones as roots.