secant method help matlab

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dulanga 2014-9-21

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评论： Alberto 2014-9-22

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hi i have been asked to make a function file for secant menthod

fxi=f(xi);

fxi_1=f(xi_1);

% Initialize iteration count iter = 1;

%iteration for the secant starts while abs(fxi)>precsion

    xi=xi-(fxi/fxi_1);
    xi_1=(xi-f(xi).(xi_1-xi))/(f(xi_1)-f(xi))
    % Increment the iteration count by 1
    iter = iter + 1;

end %the final xr value is the root root=xi; % The total iteration number iter = iter - 1; this what i have done

when i run the values its gives this error(Attempted to access f(2); index out of bounds because numel(f)=1.) can anyone help ?

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Alberto 2014-9-22

I think your code interpret f, not as a function, but as an array with values. So, when you are trying to evaluate f(x), where x=2, your code looks for the second values in an array f.

Advice: 1) save your bound points in variables a and b (for example). Also create a proper function f (inline function or m-file function), so you can evaluate f in a and b. You will need a while or for+if to make your iterations.

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