ROS Callback counter [closed]

edit

Hey there,

I need to make a node, where if a position message arrives make a vector with the actual position in x and the 4 previous values. But it doesn't work, I think is a easy code, but I am a beginner.

I cant even work with a simpler vector. I only can work with the last message position. Hope anyone can help me.

import roslib
import rospy
import math
import numpy as np
from posotion.msg import RobotPos

v = np.zeros(5)
count=0


def callback(msg):

    v[count]=msg.position
    print v


# Intializes everything
def start():
    global count
    rospy.Subscriber("robot_pos", RobotPos, callback)
    count += 1 #I also tried to use this in callback function but it doesnt work
    rospy.init_node('robot_pub') 
    rospy.spin()

if __name__ == '__main__':
    try:
        start()        
    except rospy.ROSInterruptException:
        pass