SurfLab/swarmng/logrecord__tutorial_8py_source.html

## @file logrecord_tutorial.py Tutorial for using the @ref swarmng.logrecord.LogRecord class for accessing records from a BDB log file.


# @page TutorialPythonLogRecord Examining records from the log file.

#

# The Swarm-NG log files consists of records, these records are

# encoded in binary and are accessed through swarmng.logrecord.LogRecord

# class. To get an instance of LogRecord, you would need to run a query

# on a log file and get the records in a for loop, to learn how

# to do that refer to @ref TutorialPythonQueryPlot.

#

# Source code for this tutorial can be found at @ref py/logrecord_tutorial.py


# To run the examples in this tutorial, change the code

# in @ref TutorialPythonQueryPlot to use the function defined

# here. by default the plot tutorial uses get_semi_major_axis from

# this module.

#

# The easiest way to access the planets in the log record is by

# using bodies_in_keplerian method. This methods converts the

# carteisan coordinates into Keplerian coordinates based on the

# center given. The result is an iterable object that has a 3-tuple

# as elements:

#  * first: index of the planet, starting from 1 (Note that 0 is the star)

#  * second: the original body attributes in Cartesian coordinates: contains position, velocity and mass.

#  * third: object with orbital elements as properties, refer to \ref swarmng.logrecord.keplerian_for_cartesian for a full list of attributes.

def get_semi_major_axis(l,body):

  for i, b, orbit in l.bodies_in_keplerian(center=l.star()):

    if i == body:

      return orbit.a