Don't get all rostopic echo data

edit

I have a node which publishes data 3 times. But when I look at the results of the rostopic echo, I only get the last two cycles. I have tried this with different counts, but rostopic echo always misses the first cycle.

std_msgs::Int16MultiArray head;  
ros::init(argc,argv, "xxxxxx");  
ros::NodeHandle nh;  
pubheader=nh.advertise<std_msgs>::Int16MultiArray>("Audio_head",1);  
ros::Rate loop_rate(1);  
int i,j;  
for(j=0;j<3;j++)  
{  
  head.data.clear();  
  for(i=0;i < headersize;i++)  
   {  
    head.data.push_back(header.ROSheader[i]);  
  }  
  pubheader.publish(head);  
  ros::spinOnce();  
  loop_rate.sleep();  
}

Any reason that only the last two instances are echoed?

Thanks