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readMessages

Read messages from ros2bag object

    Description

    example

    msgs = readMessages(bag) returns data from all of the messages in the ros2bag object bag. The messages are returned as a cell array of structures.

    msgs = readMessages(bag,rows) returns data from the messages in the rows specified by rows. The range of the rows is [1 bag.NumMessages].

    Examples

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    Extract the zip file that contains the ROS 2 bag log file and specify the full path to the log folder.

    unzip('alltopics.zip');
    folderPath = fullfile(pwd,'alltopics');

    Create a ros2bag object that contains all the messages in the log file.

    bag = ros2bag(folderPath);

    Get information on the contents of the ros2bag object.

    bag2info = ros2("bag","info",folderPath)
    bag2info = struct with fields:
             Path: 'C:\Users\SHIVARAD\OneDrive - MathWorks\Documents\MATLAB\Examples\ros-ex96596996\alltopics\alltopics.db3'
          Version: '1'
        StorageId: 'sqlite3'
         Duration: 102.396644003
            Start: [1×1 struct]
              End: [1×1 struct]
             Size: 4965433
         Messages: 36503
            Types: [5×1 struct]
           Topics: [5×1 struct]
    
    

    Get all the messages in the ros2bag object.

    msgs = readMessages(bag);

    Select a subset of the messages, filtered by topic.

    bagSel = select(bag,"Topic","/scan");

    Get the messages in the selection.

    msgsFiltered = readMessages(bagSel);

    Input Arguments

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    Messages in the ros2bag object, specified as a ros2bag object.

    Rows of the ros2bag object, specified as an n-element vector. n is the number of rows to retrieve messages from. Each entry in the vector corresponds to a numbered message in the bag. The range of the rows is [1 bag.NumMessages].

    Output Arguments

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    ROS 2 message data, returned as a cell array of structures.

    See Also

    Objects

    Functions

    Introduced in R2021a