Input error - finding roots of functions

I'm fairly new to matlab (only used it about 5-6 times) and am having trouble with a specific program I set up. On Wednesday it seemed to be working fine but now every time I try and use it I keep on getting the same error for every function I link it to.

Here is the text to the root finder (using the bisection method)

 function xr = root_bisect (func, xl, xu)

 %This program is designed to find the approximate roots of any function 

 %   using the Bisection Method

 %Variables

 %   xl = lower bound guess

 %   xu = upper bound guess

 %   xr = approximate root

 %   xrold = previous value of xr

 %   yl = value of the function at the lower limit

 %   yu = value of the function at the upper limit

 %   Ea = error value

 %   Es = target error (1x10^-6)

 %Prevent user from putting in two x values resulting in y values of the
 %   same sign

    if (sign(feval(func,xl)) == sign(feval(func,xu)))
        error('no root inside bracket')

    end
 %Setting target error
    Es = (10^-6);

 %Setting the initial xr

    xr = xl;

 %set initial error value to please Matlab...

    Ea = (10^12);

 %counting number of loops

    counter = 0;

 %Begin the while loop to run until Ea <= Es

    while (Ea > Es);

        %set matlab to record the previous value of xr for error
        %   calculations
        xrold = xr;
        %set the value of xr to bisect the interval
        xr = ((xl + xu)/2);

        %evaluate the functions at both guesses
        y1 = feval (func, xl);
        y2 = feval (func, xu);
        y3 = feval (func, xr);

        if ((y1)*(y3) < 0);
            %guess is too high
            xu = xr;
        elseif ((y1)*(y3) > 0);
            %guess is too low
            xl = xr;
        else ((y1)*(y2) == 0);
            %root found
            fprintf ('xr = %g \n');
            break
        end  

        %Defining error function
        Ea = abs((xr - xrold)/xr);

        %counting number of loops
        counter = counter + 1 ;
    end
    %printing number of loops to screen
    fprintf ('number of loops needed to complete calculation counter = %d \n', counter)
 end

But the error isn't showing up in there, it shows up when I link it to a function such as

 function y = funcB (x)

    y = -2+6*x-(4*(x^2))+(0.5*(x^3));

 end

When I do this I get the error

>> root_bisect (funcB,1,10)

 Error using funcB (line 2)

 Not enough input arguments.

Any help/advice would be appreciated! Thanks

Answer 1

[Matt J]

You forgot the '@'

root_bisect(@funcB,1,10)

[Lemons]

Would've been awesome if the professor explained that to me hahaah. Thanks a bunch!

[Matt J]

You're welcome. Do you know about Accept-clicking?