Getting an error stating Undefined funciton or method

I wrote this code directly out of a text as directed and then I try to run it as directed and keep getting an error that says, ??? Undefined function or method 'incsearch' for input arguments of type 'function_handle'. The code written looks like this.

 function xb = incsearch(func,xmin,xmax,ns)
%Incremental search root locator
%   xb = incsearch(func,xmin,xmax,ns):
%   finds brackets of x that contain sign changes
%   of a function on an interval
%input:
%   func=name of function
%   xmin,xmax=endpoints of interval
%   ns=number of subintervals
%output:
%   xb(k,1) is the lower bound of the kth sign change
%   xb(k,2) is the upper bound of the kth sign change
%   if no brackets found, xbb=[]
if nargin < 3 , error('at least 3 input arguments required')
end
if nargin < 4, ns=50; end % if ns is blank set to 50
% Incremental search
x=linspace(xmin,xmax,ns);
f=func(x);
nb=0;xb=[]; % xb is null unless sign change is detected
for k = 1:length(x)-1
    if sign(f(k)) ~= sign(f(k+1)) % check for sign change
        nb=nb+1;
        xb(nb,1)=x(k);
        xb(nb,2)=x(k+1);
    end
end
if isempty(xb) %display no brackets were found
    disp('no brackets found')
    disp('check interval or increase ns')
else
    disp('number of brackets:') %display number of brackets
    disp(nb)
end

The calling of it is

incsearch (@(x) sin(10*x) + cos(3*x),3,6)

and the error I keep getting is

??? Undefined function or method 'xb' for input arguments of type 'function_handle'.

I find this very funny as this is exactly how the author says to do it in the book. No wonder I am not learning much. Any help would be appreciated.

[Andrei Bobrov]

all work

Answer 1

[Jan]

I do not see a problem. Perhaps you did not save the file after editing?

A hint:

find(diff(sign(f)))

[Adam Anderson]

where in the code would I place this. I tried cutting it all off from the for loop but that produced a 1 row vector with xb=[].

Thanks for the help.