1.基本繪圖函式

plot(Y)：其中輸入引數Y就是Y軸的資料，一般習慣性輸入向量

plot(X1,Y1,LineSpec,...,Xn,Yn,LineSpec):LineSpec為選項（開關量）字串，用於設定曲線顏色、線型、資料點等；LineSpec的標準設定值見表1，前7種顏色依序（藍、綠、紅、青、品紅、黃、黑）自動著色。

plot(X1,Y1,LineSpec,'PropertyName',PropertyValue):對所有用plot函式建立的圖形進行屬性值設定，常用屬性見表2

h=plot(X1,Y1,LineSpec,'PropertyName',PropertyValue):返回繪製函式的控制代碼值h

loglog函式、semilogx函式與semilogy函式的用法與plot函式的用法類似。

clear all;
close all;
clc
M=5000;
R=[0.2 0.95];%相關矩陣
SNR=[0:2:20];
figure;
xlabel('SNR/dB','Fontsize',18);
ylabel('容量(bit/s/Hz)','Fontsize',18);
title('相關通道的容量比較','Fontsize',18)
grid on;
hold on;
for l=1:length(R)
    R_t=eye(2);
    R_r=[1 R(l);R(l) 1];
    for snr_idx=1:length(SNR)
        snr=10^(SNR(snr_idx)/10);
        for m=1:M
            Hw=(randn(2,2)+1i*randn(2,2))/sqrt(2);
            H=R_r^(.5)*Hw*R_t^(.5);
            C(m,snr_idx)=log2((det(eye(2)+snr*H*H'/2)));
        end
        Capacity(snr_idx,l)=mean(C(:,snr_idx));
    end 
end
plot(SNR,Capacity(:,1),'k -',SNR, Capacity(:,2),'kx -');

for l=1:length(R)
    R_t=eye(2);
    R_r=[1 R(l);R(l) 1];
    for snr_idx=1:length(SNR)
        snr=10^(SNR(snr_idx)/10);
        for m=1:M
            Hw=(randn(2,2)+1i*randn(2,2))/sqrt(2);
            H=R_r^(.5)*Hw*R_t^(.5);
            [gamma,eigs]=pwr_modes(H,snr);
            C(m,snr_idx)=sum(log2(real(1+eigs.*gamma*snr/2)));
        end
        Capacity(snr_idx,l)=mean(C(:,snr_idx));
    end 
end
plot(SNR,Capacity(:,1),'k - .',SNR,Capacity(:,2),'kd -');
legend('R=0 CSI未知','R=0.95 CSI未知','R=0 CSI已知','R=0.95 CSI已知','Location','Best');

dim1=[0.7 0.63 0.05 0.1];
annotation('ellipse',dim1)
annotation('arrow',[0.64 0.71],[0.71 0.71])
text(11,9,'\fontsize{18}R=0');

dim2=[0.8 0.6 0.05 0.1];
annotation('ellipse',dim2)
annotation('arrow',[0.83 0.83],[0.5 0.6])
text(18,5,'\fontsize{18}R=0.95');