Code generates one more column than needed

Hello!

I'm new to Matlab. For some reason, I can't generate 'mr' to be the same size as 'm'. 'm' comes out to be 1280 columns, whereas 'mr' is always 1281 columns.

'm' is supposed to be data of 1-0-1-0, and 'mr' is supposed to be data derived from four random bits.

Here is the relevant code:

clear all;
fs=320;           % sampling rate
ts=1/fs;          % sampling interval
fc=10;            % carrier frequency
T=4;              % total simulation time
D=1;              % data pulse duration 1s
L=D/ts;           % the number of samples for one data pulse
HL=ones(1,L);     % for logic '1'
LL=-ones(1,L);    % for logic '0'
m=[];             % set to empty vector for initiation
for i=1:T/D       % Generate the message signal
    if mod(i,2)==1
        m=[m HL];     % dump the logic '1'
    else
        m=[m LL];     % dump the logic '0'
    end
end

rnum=rand(1,4) > 0.5;
i=1;
for i=1:T/D
    for j=1:L
        if rnum(i) == 0
            mr=[m 0];
        elseif rnum(i) == 1
            mr=[m 1];
        end
    end
end

Thanks in advance for assistance!

Answer 1

[Marc Jakobi]

You have a typo in the second "mr" loop and you forgot to pre-initialize mr. So you basically either got a copy of m with a zero or a one attached, instead of an mr.

This is what it should look like:

>> fs=320;           % sampling rate
ts=1/fs;          % sampling interval
fc=10;            % carrier frequency
T=4;              % total simulation time
D=1;              % data pulse duration 1s
L=D/ts;           % the number of samples for one data pulse
HL=ones(1,L);     % for logic '1'
LL=-ones(1,L);    % for logic '0'
m=[];             % set to empty vector for initiation
for i=1:T/D       % Generate the message signal
    if mod(i,2)==1
        m=[m HL];     % dump the logic '1'
    else
        m=[m LL];     % dump the logic '0'
    end
end
rnum=rand(1,4) > 0.5;
i=1;
mr = []; %pre-initialize mr
for i=1:T/D
    for j=1:L
        if rnum(i) == 0
            mr=[mr 0]; %You had an m in the brackets mr = [m 0];
        elseif rnum(i) == 1
            mr=[mr 1];
        end
    end
end