fit a random rostopic data to a distribution over time

stats.py

import rospy
import rostopic
import sys
import scipy
import scipy.stats

data = []

def cb(msg, field):
    field = field.strip().split('.')
    datum = msg
    for f in field:
        datum = getattr(datum, f)
    data.append(datum)

def calculate(dist='norm'):
    _d = getattr(scipy.stats, dist)
    print "mu: %0.9f, stddev:  %0.9f" % _d.fit(data)

def usage():
    print """
        usage: ./stats topic_name field_name duration
    """

if __name__ == '__main__':
    if len(sys.argv) < 4:
        usage()
        sys.exit(1)

    rospy.init_node('parameter_estimator', anonymous=True)
    msg_class, real_topic, _ = rostopic.get_topic_class(sys.argv[1])
    sub = rospy.Subscriber(real_topic, msg_class, lambda s: cb(s, sys.argv[2]))
    timer = rospy.Timer(rospy.Duration(int(sys.argv[3])),
                        lambda _: (sub.unregister(),
                                   calculate(),
                                   rospy.signal_shutdown('done')),
                        oneshot=True)
    rospy.spin()