Undefined function 'bisect' for input arguments of type 'function_handle'.

Question

Alex Oard 2015-2-3

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/174955-undefined-function-bisect-for-input-arguments-of-type-function_handle

编辑： Walter Roberson 2024-3-17

I don't know why the code isn't working. We copied it from the textbook and I've checked it a dozen times and I don't know why it won't work. Any suggestions?

function [root, fx, ea, iter]=bisect(func, x1, xu, es, maxit, varargin)
% bisect: root location zeroes
%   [root, fx, ea, iter]=bisect(func, x1, xu, es, maxit, p1,p2,...):
%      uses bisection method to find the root of func
% input:
%   func = name of function
%   x1, xu = lower and upper guesses
%   es = desired relative error (default 0.0001%)
%   maxit = maximum allowable iterations (default = 50) 
%   p1,p2,... = additional parameters used by func
% output:
%   root = real root
%   fx = function value at root
%   ea = approximate relative error (%)
%   iter = number of iterations
if nargin<3, error('at least 3 input arguments required'), end
test = func(x1,varargin{:})*func(xu,varargin{:});
if test>0, error('no sign change'), end
if nargin<4|isempty(es), es=0.0001; end
if nargin<5|isempty(maxit), maxit=50; end
iter = 0; xr = x1; ea = 100;
while(1) xrold = xr;
    xr = (x1 + xu)/2;
    iter = iter + 1;
    if xr ~= 0, ea = abs((xr-xrold)/xr) * 100; end
    test = func(x1,varargin{:})*func(xr,varargin{:});
    if test < 0
        xu = xr;
    elseif test > 0
        x1 = xr;
    else 
        ea = 0;
    end
    if ea <= es | iter >= maxit, break, end
end
root = xr; fx = func(xr, varargin{:});
end

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Answer 1

Steven Lord 2024-3-17

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/174955-undefined-function-bisect-for-input-arguments-of-type-function_handle#answer_1426581

Another possibility is that the user saved it to a file not named bisect.m. If the name of a function file and the name of the main (first) function in that function file differ, MATLAB will only be able to call the function when you use the file name not the function name. That's one of the reasons why we recommend that for function files you use the same name for the file (but add the .m extension) and the function (no extension.)