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Plotting covariance from amcl_pose in Matlab

asked 2020-03-05 02:16:37 -0500

fendrbud
48 ●9 ●11 ●18

updated 2020-03-05 02:17:29 -0500

I have recorded a bag-file and am trying to plot the /amcl_pose/pose/covariance matrix which has a message type geometry_msgs/PoseWithCovarianceStamped. I followed this tutorial on plotting data from topics, however, when I try:

bagselect = select(bag, 'Topic', '/amcl_pose');
msgs = readMessages(bagselect);
ts = timeseries(bagselect, 'Pose.Covariance');

I Get the error:

The Pose.covariance property does not exist for message type geometry_msgs/PoseWithCovarianceStamped.

What am I doing wrong?

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answered 2020-03-05 02:46:02 -0500

fendrbud
48 ●9 ●11 ●18

updated 2020-03-05 02:46:29 -0500

I found out I have to read the messages as structures as in this example.

bSel = select(bag, 'Topic', '/amcl_pose');
msgStructs = readMessages(bSel, 'DataFormat', 'struct');

I am then able to read amcl_pose as a struct and can then extract the first covariance matrix by

msgStructs{1}.Pose.Covariance

I now have to iterate through all the matrices and concatenate them in order to plot their values.

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I've converted your comment to an answer as it would appear this is the answer.

To link it to my comment about the covariance field not being at the top-level of the message (but at pose.pose.covariance: it would appear msgStructs{1} contains the top-level message contents. So then pose.covariance does exist there.

gvdhoorn ( 2020-03-05 02:58:40 -0500 )edit

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Asked: 2020-03-05 02:16:37 -0500

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Last updated: Mar 05 '20

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Plotting covariance from amcl_pose in Matlab