Error in the for loop in matlab

Question

I try to plot from for loop and I succeed in it(in small program) but when i try with a larger program, I get the following error: "{Error using ==> semilogy Not enough input arguments. Error in ==> test6 at 27 semilogy(pe1,'b',pe2,'r');} and i dont why I wish someone can have a look and help me

my code is

clc;
clear;
for n=0:45;

    n=n+1;
   q=55;
    w=42;
    r=-228.6;
    y(n+1)=n+34+w-q-r;
end 

b=36;
o=0.2;
x=b/(1+o);                        % RB for Bpsk
k=2*b/(1+o);                      % Rb for Qpsk
z=y-x;                            % Eb/No for Bpsk
m=y-k;                            % Eb/No for Qpsk
g=0; 
s=0;  
pe1= zeros(1, 47);
pe2= zeros(1, 47);

for i=0:45; 
    g=10.^(0.1*z);
    pe1=0.5*erfc(sqrt(g));
    s=10.^(0.1*m);
    pe2=0.5*erfc(sqrt(s));
end

semilogy(pe1,'b',pe2,'r');
xlabel('energy per bit per noise power spectral density (Eb/No) (dB) ');
ylabel('Bit error rate (Pe)');
legend('Bpsk','Qpsk');
grid;

I don't want to moralize, but your variable naming convention is awful I can't imagine returning to such code after a week or heavens forbid a month. Bunch of unnamed constants, one letter variable names. Get a grip man :) — Biggles
– Biggles, Commented May 19, 2011 at 12:33
sorry for my awful cod but im new in matlab programming so l try do my best to work with this program if you have more tips you can told me , this will be nice (more help in code) — ash210
– ash210, Commented May 20, 2011 at 16:30
if you have any knowledge about Qpsk,Bpsk modulation this will help me — ash210
– ash210, Commented May 20, 2011 at 16:32

Ramashalanka · Accepted Answer · 2011-05-19 08:27:28Z

The problem causing your error is that semilogy (like plot) expects inputs in the form semilogy(X1,Y1,'b',X2,Y2,'r') if you want to plot more than one line at the same time. So, your semilogy should be semilogy(z,pe1,'b',m,pe2,'r'). You also need the z and m in the semilogy call to get your x-axis scale correct.

You have a few other problems. I have not made it look exactly like I'd do it, since I wanted your code to be recognizable to you. But you may wish to compare your code line by line to the following. One thing I've done that is probably wrong is change r to its negative since otherwise y is far to large (so pe1 and pe2 were zero, via erfc).

Your code was already vectorized, so I got rid of the for loops. Note that you wouldn't have n=n+1 in a for n= loop; it's incremented automatically.

clc;
clear;
n=0:45;
q=55;
w=42;
r=228.6;
y=n+34+w-q-r;

b=36;
o=0.2;
x=b/(1+o);                        % RB for Bpsk
k=2*b/(1+o);                      % Rb for Qpsk
z=y-x;                            % Eb/No for Bpsk
m=y-k;                            % Eb/No for Qpsk

g=10.^(0.1*z);
pe1=0.5*erfc(sqrt(g));
s=10.^(0.1*m);
pe2=0.5*erfc(sqrt(s));

semilogy(z,pe1,'b',m,pe2,'r');
xlabel('energy per bit per noise power spectral density (Eb/No) (dB) ');
ylabel('Bit error rate (Pe)');
legend('Bpsk','Qpsk');
grid;

Collectives™ on Stack Overflow

Error in the for loop in matlab

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related