subscriber

#include <ros/ros.h>
#include <tf/transform_listener.h>
#include <iostream>
#include <nav_msgs/Odometry.h>

using namespace std;
/*#include <turtlesim/Velocity.h>
  #include <turtlesim/Spawn.h>*/

// %Tag(CALLBACK)%

void chatterCallback(const nav_msgs::Odometry::ConstPtr& msg)
{
  ROS_INFO("I heard: [%f]", msg->pose.pose.position.x);
}


int main(int argc, char** argv){
  ros::init(argc, argv, "my_tf_listener");

  ros::NodeHandle node;

  // ros::service::waitForService("odom");
 /* ros::ServiceClient add_turtle =
       node.serviceClient<turtlesim::Spawn>("spawn");
  turtlesim::Spawn srv;
  add_turtle.call(srv);

  ros::Publisher turtle_vel =
       node.advertise<turtlesim::Velocity>("turtle2/command_velocity", 10);
*/
  tf::TransformListener listener;
   ros::Subscriber sub = node.subscribe("odom", 1000, chatterCallback);
ros::spin();
  ros::Rate rate(1.0);
  while (node.ok()){
    tf::StampedTransform transform;
       try{
      listener.lookupTransform("tf", "odom",
                               ros::Time::now(), transform);
    }
    catch (tf::TransformException ex){
      ROS_ERROR("%s",ex.what());
      }
    cout << transform.getOrigin().y()<<endl;
    cout << transform.getOrigin().x()<<endl;
//    turtlesim::Velocity vel_msg;
/*    vel_msg.angular = 4 * atan2(transform.getOrigin().y(),
                                transform.getOrigin().x());
    vel_msg.linear = 0.5 * sqrt(pow(transform.getOrigin().x(), 2) +
                                 pow(transform.getOrigin().y(), 2));
    turtle_vel.publish(vel_msg);*/

    rate.sleep();
  }
  return 0;
};