readMessages

Read messages from ros2bagreader object

Since R2021a

Syntax

msgs = readMessages(bag)

msgs = readMessages(bag,rows)

Description

msgs = readMessages(bag) returns data from all of the messages in the ros2bagreader 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

Read Messages from ROS 2 Bag Log File

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

unzip("ros2_netwrk_bag.zip");
folderPath = fullfile(pwd,"ros2_netwrk_bag");

Create a ros2bagreader object that contains all the messages in the log file.

bagReader = ros2bagreader(folderPath);

Get information about the contents of the ros2bagreader object.

baginfo = ros2("bag","info",folderPath)

baginfo = struct with fields:
         Path: 'C:\Users\ros2_netwrk_bag\ros2_netwrk_bag.db3'
      Version: '1'
    StorageId: 'sqlite3'
     Duration: 207.9020
        Start: [1×1 struct]
          End: [1×1 struct]
         Size: 16839538
     Messages: 166867
        Types: [4×1 struct]
       Topics: [4×1 struct]

Get all the messages in the ros2bagreader object.

msgs = readMessages(bagReader);

Select a subset of the messages, filtered by topic.

bagSel = select(bagReader,"Topic","/odom")

bagSel = 
  ros2bagreader with properties:

           FilePath: 'C:\Users\ros2_netwrk_bag'
      AvailableBags: "ros2_netwrk_bag.db3"
          StartTime: 1.6020e+09
            EndTime: 1.6020e+09
    AvailableTopics: [1×3 table]
    AvailableFrames: {0×1 cell}
        MessageList: [5275×3 table]
        NumMessages: 5275

Get the messages in the selection.

msgsFiltered = readMessages(bagSel);

Input Arguments

bag — Messages in ros2bagreader object

ros2bagreader object

Messages in the ros2bagreader object, specified as a ros2bagreader object.

rows — Rows of ros2bagreader object

n-element vector

Rows of the ros2bagreader 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

msgs — ROS 2 message data

cell array of structures

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

Version History

Introduced in R2021a