How to extract data from sensor_msgs/Joy ROS as timeseries in MATLAB script?

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Thanks for your help. I am working with rosbag files in MATLAB R2016B. Following the examples in I try to extract data from sensor_msgs/Joy from an specific topic like this:
bagselection_setpoint_attitude = select(bag,'Topic','/controlbot/joystick');
ts_setpoint_attitude = timeseries(bagselection_setpoint_attitude);
When I type ts_setpoint_attitude.Data the answer is:
ans =
0 0 0
1 0 0
2 0 0
3 0 0
4 0 0
5 0 0
6 0 0
But this type of messages contains Header, Axes and Buttons. If I use the following code:
test = readMessages(bagselection_setpoint_attitude)
The result is:
test =
946×1 cell array
[1×1 Joy]
[1×1 Joy]
[1×1 Joy]
[1×1 Joy]
[1×1 Joy]
[1×1 Joy]
[1×1 Joy]
[1×1 Joy]
[1×1 Joy]
[1×1 Joy]
[1×1 Joy]
If I go into each cell, the property Axes which is that I need, show the correct values:
ans =
4×1 single column vector
Why when I work with timeseries, the data is not visualized correctly? In fact the size of timeseries columns is not correct?
How can I access to Axes data from this type of message successfully?
Best Regards

Answers (1)

MathWorks Robotics and Autonomous Systems Team
Edited: Walter Roberson on 16 Jan 2024
As shown in the example:
filepath = fullfile(fileparts(which('ROSWorkingWithRosbagsExample')), 'data', 'ex_multiple_topics.bag');
bag = rosbag(filepath);
bagSelection = select(bag,'Topic','/odom');
ts = timeseries(bagSelection,'Pose.Pose.Position.X');
There was only one topic in the "bagSelection" variable, and then only one data from Pose data was extracted and was put in timeseries fashion.
Follow a similar pattern and you will be able to extract the data you are looking for.
  1 Comment
Kyle Gao
Kyle Gao on 15 Jan 2024
Hi, can you please eleborate more? Odom data is a structure where the x position can be directly accessed by 'Pose.Pose.Position.X'. However, button in /joy topic is a list of numbers. It seems the timeseries function can not associate a timeseries to a list but rather a single value. Thanks in advance

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