How does this code plot eye diagram?

hi guys
below is the code of bpsk where eye diagram is plotted. i want to know how does this plots eye diagram.
zeros create matrix of zeros....but what about the second last line what does it do and on what basis the values(1001:1000+700*1000) are selected and how does this plots eye diagram...please explain as i have tried to figure it out but couldnt understand the logic behind this....
thnx




x=-1 + 2 * round(rand(1,16000)); %generating -1 and 1(BPSK symbols)
x_in=upsample(x_k,100);
a=sqrt(100)*firrcos(255,0.01,1,2,'rolloff','sqrt');

xt_Tx=filter(a,1,x_in);
c_t=[1 0]; %ideal channel impulse response
xt=filter(c_t,1,xt_Tx);
xt_Rx=filter(a,1,xt);
EYE = zeros(700,1000);
EYE[:] =xt_Rx(1001:1000+700*1000);
plot(EYE);

Re: eye diagram

The reason that the beginning 1000 data points are omitted in the receiver side is
that filter delay should be considered and thoses beginning points should be deleted .

EYE = zeros(700,1000);
EYE[:] =xt_Rx(1001:1000+700*1000);

These two lines indicates that EYE is a 700*1000 matrix and its elements value are xt_Rx(1001:1000+700*1000) in collum wise, which means rearrange xt_rx(1001:1000+700*1000) in 700*1000 matrix form. That's the origin of eye-diagram: overlap data symbol one by one in a single symbol period and observe the eye.