test newton

function [ ] = newton(func, a, b, delta, maxd )
%UNTITLED Summary of this function goes here
%   Detailed explanation goes here
funcd1 = diff(func,1);
funcd2 = diff(func,2);
eps = 10^-delta;
set = 0;
x0 = 0;
if a > b
    [a,b] = deal(b,a);
end

if subs(func,a)*subs(funcd2,a) > 0
    x0 = a;
    set = 1;
else
    if subs(func,b)*subs(funcd2,b) > 0
        x0 = b;
        set = 1;
    end
end

if set == 0
    for i=a:eps:b
        if subs(func,i)*subs(funcd2,b) > 0
            x0 = i;
            set = 1;
        end
    end
end

if set == 0
    sprintf('Nie mozna znalezc punktu spelniajacego warunek f(x)*f"(x)>0!');
    return
else
    sprintf('Znaleziono x0=%f',x0)
end

xk = x0;
xk1 = x0 - subs(func,x0)/subs(funcd1,x0);
d = 0;
while abs(subs(func,xk1)) > eps && d < maxd
    d = d+1;
    xk = xk1;
    xk1 = xk - subs(func,xk)/subs(funcd1,xk);
    if abs(xk1-xk) <= eps || abs(subs(func,xk1)) <= eps
        break
    end
end

if d == maxd
    sprintf('Nie znaleziono miejsca zerowego w zadanym przedziale po %d przejsciach',maxd)
else
    sprintf('x0 = %f',xk);
end

end