Passing functions in MATLAB

Hi I am having some difficulty passing functions on MATLAB and needed some help.

I am trying to implement a bisection algorithm, [l,r,nf] = bisect ( fname, a,b, tol)

Where l and r are the left and right handed end-points of the root-bracketing interval, and fname is another M-file in my directory that contains the actual function being evaluated (also an M-file)

How does one use a function as the input for an argument in MATLAB? Thanks!

Answer 1

[dpb]

Look at function handles; there's a section under Data Types in the documentation...

[Shakil Rafi]

Hi so suppose I want to use @ to call the function, I am unclear what my code would look like then.

Would it be something like

[l,r,nf] = bisect (@fname, a,b,tol)

if @fname(a) * @fname(b) > 0 
      disp (' Function does not bracket a root');
      ...

or

[l,r,nf] = bisect (fname, a,b,tol)

if @fname(a) * @fname(b) > 0 
      disp (' Function does not bracket a root');
      ...

or

[l,r,nf] = bisect (@fname, a,b,tol)

if fname(a) * fname(b) > 0 
      disp (' Function does not bracket a root');
      ...

because all three of these seem to not work.

And when i want to test them out in the command window, how would i test out the function? would it be bisect(fofx,1,2,0.0001) or bisect (@fofx,1,2,0.001)

Thanks

[Walter Roberson]

 function [l,r,nf] = bisect ( fname, a, b, tol)
   if fname(a) * fname(b) > 0
   [...]

To be called with something like

[left, right, count] = bisect( @(x) sin(x).^2 - tan(x), -pi/2, pi/2, 0.01 )