problem when copying a plot line to another

I am new to Matlab.

Can anyone help me with the problem when I copy the graph line of the BPSK to the plot of the BFSK, the pasted BPSK has wrong x-axis values. The red lline must cross the x-axis at 9.6.

thanks in advance for any help!

[Osama Al-Shalali]

This is how must BPSK look like.

[Geoff Hayes]

Osamam - could you show us the code that you are using to copy the plot from one figure to the other?

[Osama Al-Shalali]

This is the code gor the copied plot

close all; clc;

num_bits = 300000; % signal lenghth
max_run = 10;    % maximum number of iterations for a single SNR
Eb = 1;          % bit energy
k=1; n=1;
R=k/n;             % the rate 
SNR_db = 0:0.5:13;  % signal to noise ratio in db
SNR = 10.^(SNR_db/10);
hand = waitbar(0,'Simulation is being processed,please wait...');
for count = 1:length(SNR)  % begining of loop for different SNR, all SNR
    avgError = 0;
    sigma=sqrt((Eb/(2*R*SNR(count))));
  for run_time=1:max_run  % begining of loop for different runs
    waitbar((count*max_run)/(length(SNR_db)*max_run));
    Error = 0;
    data = randi([0 1],1,num_bits);   % generate binary data source
    S = 2*data-1;                 % baseband BPSK modulations
    N = sigma*randn(1,num_bits); % generate AWGN
    Y  = S+N;                      % Received noist signal
    for k = 1:num_bits % Decision device taking hard decision and deciding error
     if ((Y(k)>0 && data(k)==0)||( Y(k)<0 && data(k)==1))
         Error=Error+1;
     end
    end
 Error=Error/num_bits;  % caulculate error/bit
 avgError=avgError+Error;  % caulculate error/bit for different runs
 end                        % Termination of loop for differwnt runs
BER_sim(count)=avgError./max_run;  % calculate BER for a particular SNR
end   % Termination of loop for differnet SNR
BER_th=(1/2)*erfc(sqrt(SNR)); % calculate the analytical BER
close(hand);
semilogy(SNR_db,BER_th,'r');% you can change the graph style r-* or r-o or r-x
grid on
hold on
%semilogy(SNR_db,BER_th_coded,'g');
hold on
semilogy(SNR_db,BER_sim,'b*');
title('PBSK under AWGN simulation and theoritcal');
xlabel('Eb/No (dB)')
ylabel('Bit Error Rate')
legend('Theortical','Simulation','location','SouthWest');
axis ([min(SNR_db) 10 10^(-5) 10^(-1)]);
hold off

[Walter Roberson]

You are using a log y plot. It cannot cross the x axes, because crossing the x axes would be y=0 which would be infinitely far down because of the log scale.

[Renato SL]

I think he meant literally 'crossing' as in 'visually touching' the x-axis at 9.6, not to cross y=0

In my opinion, this is an issue on setting the minimum value for the y-axis (ymin). The values plotted in red line and blue stars look the same for me.

[Osama Al-Shalali]

Thanks so much! I got it.

becasue the y axsis is not the same for both graphs, the problem occured.