Right code for Centred finite difference?

Is this the right code to find the Centred finite difference and plot it on a graph? My plot looks wrong. The centred difference is in yellow

y=2*cos(3*x)-x.^2+7*x-6;
diff(y,x)
dydx_actual=diff(y,x)
clear x
h=0.1;
x=0:h:6;
%CFD
dydx_cfd=(y(3:end)-y(1:end-2))./h;
plot(x(2:end-1),dydx_cfd,'y')