Coding a function to find zeros using a variant of the bisection/secant method

Hello, I have a programming assignment where I have to implement a matlab function that is a variant of the bisection and secant method. Please see attachment for exact details. I am having problems with the code. Will someone help me with the necessary fixes? My code is as follows: —————————————————————————————————————-

if true
  % code
function p = bisection(f, a, b, tol)
w=1;
for i=1:100
  p= a +(w*f(a)*(a-b)/f(b)-w*f(a));
  fprintf(a,b,p,f(p));
  if f(p)*f(b)>0
      w=0.5;
  else
      w=1;
      a=b;
  end
  b=p;
  if abs(b-a)<tol
      abs(f(p))<tol
      break;
  end
end.

Answer 1

[Walter Roberson]

No, no error about needing to use () . However,

output = bisection(@(x) sin(x)+3*cos(x).^2, -pi/2, pi/2, 1e-5)

Error using fprintf
Invalid file identifier. Use fopen to generate a valid file identifier.

Error in solution>bisection (line 7)
fprintf(a,b,p,f(p));

function p = bisection(f, a, b, tol)
w=1;
for i=1:100
    p= a +(w*f(a)*(a-b)/f(b)-w*f(a));
    fprintf(a,b,p,f(p));
    if f(p)*f(b)>0
        w=0.5;
    else
        w=1;
        a=b;
    end
    b=p;
    if abs(b-a)<tol
        abs(f(p))<tol
        break;
    end
end
end

This is because the first parameter to fprintf must be one of:

1. A file identifier
2. A format character vector or format string scalar
3. A device object for some kinds of devices such as serialport objects

The first parameter you are passing is a, which is numeric but is not a valid file identifier.

[Lavorizia Vaughn]

What should I do to fix this issue?

[Walter Roberson]

You should pass a format character vector as the first parameter to fprintf()

[Lavorizia Vaughn]

Ok, how do I do that? I’m sorry but I’m a super beginner at matlab

[Walter Roberson]

https://www.mathworks.com/help/matlab/ref/fprintf.html#btf8xsy-1_sep_shared-formatSpec

[Lavorizia Vaughn]

Yeah dude, I’m still kind of lost. You mind telling me exactly what to change?

[Walter Roberson]

    fprintf('Lovorizia, the value for a was %g .\nAnd b was %g .\n, Then there was p, which was %g .\n And lastly, if you still care, f(p) was %g .\n', a, b, p, f(p));