Constellation Diagram for Binary QPSK

This program is used to plot a constellation diagram for QPSK

function[y] = Constellation_QPSK()
M =4;
i = 1:M;
y = cos((2*i-1)*%pi/4)-sin((2*i-1)*%pi/4)*%i;
annot = dec2bin([0:M-1],log2(M));
disp(y,'coordinates of message points')
disp(annot,'dibits value')
figure;
a =gca();
a.data_bounds = [-1,-1;1,1];
a.x_location = "origin";
a.y_location = "origin";
plot2d(real(y(1)),imag(y(1)),-2)
plot2d(real(y(2)),imag(y(2)),-4)
plot2d(real(y(3)),imag(y(3)),-5)
plot2d(real(y(4)),imag(y(4)),-9)
xlabel('                                             In-Phase');
ylabel('                                             Quadrature');
title('Constellation for QPSK')
legend(['message point 1 (dibit 10)';'message point 2 (dibit 00)';'message point 3 (dibit 01)';'message point 4 (dibit 11)'],5)
endfunction
//Result
//coordinates of message points   
//  0.7071068 - 0.7071068i  - 0.7071068 - 0.7071068i  - 0.7071068 + 0.7071068i    0.7071068 + 0.7071068i  
// 
// dibits value   
// 
//!00  01  10  11  !