timing.py

#!/usr/bin/env python

import rospy
from sensor_msgs.msg import Imu

import numpy as np
import matplotlib.pyplot as plt

class Timing():
    def __init__(self):

        self.count = 0
        self.arrivals = []
        self.stamps = []

        self.imu_sub = rospy.Subscriber('imu/data', Imu, self.imuCallback, queue_size=1)

        while not rospy.is_shutdown():
            rospy.spin()

    def imuCallback(self, msg):
        self.arrivals.append(rospy.Time.now().to_sec())
        self.stamps.append(msg.header.stamp.to_sec())
        self.count += 1

        if self.count >= 1000:
            rospy.signal_shutdown("Received IMU measurements")

if __name__ == '__main__':
    rospy.init_node('timing')
    timing = Timing()

    # plot results
    plt.figure(1)

    plt.subplot(211)
    plt.hist(np.diff(timing.arrivals), bins=50)
    plt.title('Arrival Times')

    plt.subplot(212)
    plt.hist(np.diff(timing.stamps), bins=50)
    plt.title('Stamp Times')

    plt.figure(2)

    plt.subplot(211)
    plt.plot(timing.arrivals[1:], np.diff(timing.arrivals))
    plt.title('Arrival Times')

    plt.subplot(212)
    plt.plot(timing.stamps[1:], np.diff(timing.stamps))
    plt.title('Stamp Times')

    plt.show()