MATLAB: Determining the 4th degree polynomial

polynomial

I need help about determine the 4th degree polynomial y(x) that passes through the following points:

(0,−1), (1, 1), (3, 3), (5, 2) and (6,−2).

polyfit([0 1 3 5 6], [-1 1 3 2 -2], 4)

If you need symbolic form you could poly2sym() the result of the above.

Try this( Symbolic Toolbox is required for this code):

v = fliplr([2 -3 +4 -5]);
syms x;
fun(x)=sym(0);
for i=1:numel(v)
    fun(x)=fun(x)+v(i)*x^(i-1);
end

r = roots([a,b,c,d,e]);
r(imag(r)~=0) = [];  %remove complex
r(r <= 0) = [];  %remove non-positive
min(r)  %now it is the smallest positive real root