How do I plot the square of the amplitude response?
If the impulse response $$h[n]=\delta[n]+\alpha \delta[n-R]\hspace{1cm}=\{1,0,0,...\alpha\}$$ with the ellipsis being R presumably, the Fourier transform $$H(\omega)=e^{-j 0 \omega}+\alpha e^{-jR \omega}=1+\alpha e^{-jR \omega}\hspace{1
cm}\exists\hspace{1
cm}\mathbb{C}$$
where magnitude is defined as $\sqrt{x^{2}+y^{2}}=|x+iy|$  

Since we want the square of the amplitude response $=|H(\omega)|^2$, we can square the real and imaginary parts of the transform$$\Re{\{H(\omega)\}}^{2}+\Im{\{H(\omega)\}}^{2}\hspace{.5cm}=\hspace{.5cm}(1+\alpha \cos(-R\omega))^{2}+\alpha \sin(-R\omega)^2\hspace{.5cm}\exists\mathbb{R}$$
Then plot from $\omega=[0,\pi)$  

Might look something like this with your parameters


Please tell me if this gives the expected response because I'm relatively new to continuous/algebraic Fourier theory