zadatakMatlab

function x = Powell( f,x0,err )
%UNTITLED Summary of this function goes here
%   Detailed explanation goes here

d1 = [1;0];
d2 = [0;1];
xlast = x0;

while 1
    ftemp = @(x) f((xlast + x*d1)');
    xcur = xlast + amaterMin(ftemp,-100,100,0.01)*d1;

    ftemp = @(x) f((xcur + x*d2)');
    xnew = xcur + amaterMin(ftemp,-100,100,0.01)*d2;

    d3 = xnew - xlast;

    ftemp = @(x) f((xnew+x*d3)');
    xnewnew = xnew + amaterMin(ftemp,-100,100,0.01)*d3;

    if xlast - xnew < [err;err]
        x = xnew;
        return;
    end

    xlast = xnewnew;
    d1 = d2;
    d2 = d3;

end

    function rez = amaterMin(fun,a,b,step)
        x1 = a;
        x2 = a + step;
        x3 = a + step + step;
        for xi = a:step:b
            if (fun(x1) > fun(x2) && fun(x2) < fun(x3))
                rez = x2;
                return;
            end
            x1 = x1+step;
            x2 = x2+step;
            x3 = x3+step;
        end
        if fun(a) >= fun(b)
            rez = b;
        else
            rez = a;
        end
    end

end