matlab : polynomial fitting

octave-3.2.3:4> for i = 1 : 51
> x(i) = .2*(i - 1);
> end


octave-3.2.3:6> for i = 1: 51
> y(i) = 1 - x(i);
> end

octave-3.2.3:8> polyfit(x,y,4)
ans =

   1.1249e-17  -2.3654e-16   1.7285e-15  -1.0000e+00   1.0000e+00