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--- logging_tutlesim [2013/06/25 13:07] – created bokal
+++ logging_tutlesim [2016/05/19 09:19] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
-===== Logging ''turtlesim'' data =====
+===== Logging turtlesim data =====
 This is a simple example to show logging of pose and velocity information from running the ''turtlesim'' node.
 ==== Logging the data ====
 Start the turtlesim and log all the topics using the following sets of commands
-  rosrun turtlesim turtlesim
+  rosrun turtlesim turtlesim_node
-  rosrun turtlesim turtle_tel # for keyboard teleop to get changing data
+  rosrun turtlesim turtle_teleop_key # for keyboard teleop to get changing data
-  rosrun mongodb mongodb_log -a # for all topics. check help for more options
+  rosrun mongodb_log mongodb_log -a # for all topics. check help for more options
   # use Ctrl + C to stop
 ==== Accessing the data ====
-The data that has been logged can be accessed via may ways, directly using terminal mongo client or via the language APIs.
+The data that has been logged can be accessed via may ways, directly using terminal mongo client or via the language APIs. These are each shown below;
+=== Via the mongo terminal client ===
+This is installed when you get the mongodb package installed on the system.
+   mongo # alternatively, use the ros version with rosrun mongodb mongo
+   # you should see an interface like the following
+   MongoDB shell version: 2.0.4
+   connecting to: test
+   # change to the ros database using
+   > use roslog
+   switched to roslog
+   # see a list of databases using
+   > show dbs
+   local	(empty)
+   roslog	0.203125GB
+   # see the list of items stored using the following
+   > db.getCollectionNames()
+   [
+    	"system.indexes",
+    	"turtle1_color_sensor",
+    	"turtle1_command_velocity",
+    	"turtle1_pose"
+   ]
+   # further commands are given in standard mongo cheatsheets
+   >
+=== Via a python API ===
+The full documentation of the python API is available online at [[http://api.mongodb.org/python/current/|http://api.mongodb.org/python/current/]]. Below is a simple example usage:
+  import pymongo
+  mclient = pymongo.Connection()
+  db = mclient['roslog']
+  # get the collections
+  db.collection_names()
+  [u'turtle1_color_sensor', u'system.indexes', u'turtle1_pose', u'turtle1_
+  command_velocity']
+  # show all the data in the database
+  docs = db['turtle1_pose'].find()
+  for d in docs:
+    print d
+  # this displays a long list with elements like these
+  {u'__topic': u'/turtle1/pose', u'linear_velocity': 0.0, u'theta': 1.9824
+  440479278564, u'y': 8.26992130279541, u'x': 4.029432773590088, u'_id': O
+  bjectId('51c98fcca6c646570b000901'), u'angular_velocity': 0.0, u'__recor
+  ded': 1372164044.44448}
+  {u'__topic': u'/turtle1/pose', u'linear_velocity': 0.0, u'theta': 1.9824
+  440479278564, u'y': 8.26992130279541, u'x': 4.029432773590088, u'_id': O
+  bjectId('51c98fcca6c646570b000902'), u'angular_velocity': 0.0, u'__recor
+  ded': 1372164044.460494}
+  # querying can be done directly on these. e.g.
+  q = db['turtle1_pose'].find({'__recorded':{'$gt' : 1372164044.44448}})
+  q.count()
+# which is exactly the last recording as shown in the data snippet above