Tukey window in time domain

I am trying to implement Tukey window in time domain. It is the rectangular filter where the edges are tapered by convolving a rectangular function with a cosine lobe.

given by formula:

I think I am doing something wrong here. Need help.

alpha = 0.5;

N = 2048;    
Ts = 0.01;
time = -20: Ts: (N-1) * Ts;    % -20sec t0 20sec

% rectangular window
x = zeros (size (time));

for n = 1: length (time)
if time (n)> - (1-alpha) / 2 && time (n) <(1-alpha) / 2
 x (n) = 1;
end
end
figure (1)
plot (time, x);



% cosine window
y = zeros (size (time));
for n = 1: length (time)
if time (n)> = (1-alpha) / 2 && time (n) <= (1 + alpha) / 2
    y = (1/2) + (1/2) * cos (pi / alpha (abs (time) - ((1-alpha) / 2)));
end
end
plot (time, y);

[Darshan Ramakant Bhat]

https://in.mathworks.com/help/signal/ref/tukeywin.html