Help me with this error ?

I downloaded this file from file exchange (fixedpoint iteration method find approximate root of nonlinear equation). But I don't understand why it have this error(the success variable). Help me to fix it ? . thanks very much.

Answer 1

[Star Strider]

There seems to be a logic problem in the fixedpoint function.

I don’t usually suggest altering others’ code, but it might be worthwhile to experiment by inserting between these lines:

P0 = p0;

% STEP 1

the line:

success = false;

so that it reads:

P0 = p0;

success = false;

% STEP 1

I cannot guarantee that it will find the real root of your function, since I haven’t run the fixedpoint function or your code with it.

When I used the core MATLAB function roots on your polynomial:

r = roots([1 2 0 -5])

it had one real negative root and two complex roots:

r =

      -1.6209e+000 +  1.1826e+000i
      -1.6209e+000 -  1.1826e+000i
       1.2419e+000 +             i