converting the fzero function of MATLAB (Brent Method) to C code -


i trying write similar function in c 1 in matlab called fzero, found out fzero uses brent method in order find roots.

t=fzero(myfunction,cathreshold);

this function need, suppose give me 0 of myfunction near cathreshold.

when tried implement brent method in order find required result figured out in addition myfunction need 2 inputs a , b.

b considered current guess root of myfunction. a point such myfunction(a) , myfunction(b) have opposite signs, interval [a, b] contains solution.

i can write c code of brent method knowing inputs couldn't write 1 knowing function, , called cathreshold. how should choose value of a ?!

could explains me how fzero works maybe help!

from documentation of fzero(fun,x0), can see x0 should within interval [a,b] such f(a) , f(b) have different signs.

by typing edit fzero in command window, can open function itself. may write own version, looking through non-obfuscated code. @ top of function see description:

%   x = fzero(fun,x0) tries find 0 of function fun near x0,  %   if x0 scalar.  first finds interval containing x0  %   function values of interval endpoints differ in sign, searches  %   interval zero.

so fzero still uses interval [a,b], finds interval surrounding scalar x0. note can pass interval fzero, detailed second input option:

%   x = fzero(fun,x0), x0 vector of length 2, assumes x0  %   finite interval sign of fun(x0(1)) differs sign of  %   fun(x0(2)). error occurs if not true.

specifically, see part of function begins

% interval input

where see processing of 2 above input options

if (numel(x) == 2)      % ...     = x(1); savea=a;     b = x(2); saveb=b;     % ...  elseif (numel(x) == 1)     % ...     % method calculating , b     % ... end

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