please help me in ploting the modulated signal.

clear; clc;
data_size=10;
M=2;
freq_sep=250;
nsamp=10;
fs=500;
data=randi([0 1],1,data_size);
qam_mod=qammod(data,M);
qam_demod=qamdemod(qam_mod,M);
ln=length(qam_mod);
subplot(2,1,1)
stairs(data)
AXIS([0 data_size -2 2])
xlabel('TIME')
ylabel('AMPLITUDE')
title('SENT DATA')
subplot(2,1,2)
stairs(qam_demod)
AXIS([0 data_size -2 2])
xlabel('TIME')
ylabel('AMPLITUDE')
title('RECEIVED DATA')

%time=0:1/fs:data_size*nsamp*1/fs-1/fs;
figure
subplot(2,1,1)
plot(qam_mod)
%axis([0 data_size*nsamp*1/fs -2 2 ])
grid  on;
subplot(2,1,2)
stairs(data)
AXIS([0 data_size -2 2])
[num,rate]=biterr(data,qam_demod)

[Walter Roberson]

What difference do you see between what you get and what you expect to get? Are you encountering an error message?