select

Select subset of messages in ros2bag

Syntax

bagsel = select(bag)

bagsel = select(bag,Name,Value)

Description

bagsel = select(bag) returns a ros2bag object, bagsel, that contains all of the messages in the ros2bag object, bag.

This function creates a copy of the ros2bag object or returns a new ros2bag object that contains the specified message selection.

bagsel = select(bag,Name,Value) provides additional options specified by one or more name-value pair arguments. For example, "Topic","/scan" selects a subset of the messages, filtered by the topic /scan.

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 ros2bag object that contains all 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: '/tmp/Bdoc22a_1891349_146723/tp4bb54338/ros-ex96596996/ros2_netwrk_bag/ros2_netwrk_bag.db3'
      Version: '1'
    StorageId: 'sqlite3'
     Duration: 207.9020
        Start: [1x1 struct]
          End: [1x1 struct]
         Size: 16839538
     Messages: 166867
        Types: [4x1 struct]
       Topics: [4x1 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","/odom");

Get the messages in the selection.

msgsFiltered = readMessages(bagSel);

Input Arguments

bag — Messages in ros2bag object

ros2bag object

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

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: select(bag,"Topic","/scan") selects a subset of the messages, filtered by the topic /scan.

MessageType — ROS 2 message type

string scalar | character vector | cell array of string scalars | cell array of character vectors

ROS 2 message type, specified as a string scalar, character vector, cell array of string scalars, or cell array of character vectors. Multiple message types can be specified with a cell array.

Example: select(bag,"MessageType",{"sensor_msgs/CameraInfo","sensor_msgs/LaserScan"})

Data Types: char | string | cell

Time — Start and end times of ros2bag selection

n-by-2 vector

Start and end times of the ros2bag selection, specified as an n-by-2 vector.

Example: select(bag,"Time",[bag.MessageList(1,1).Time,bag.MessageList(2,1).Time])

Data Types: uint64

Topic — ROS 2 topic name

string scalar | character vector | cell array of string scalars | cell array of character vectors

ROS 2 topic name, specified as a string scalar, character vector, cell array of string scalars, or cell array of character vectors. Multiple topic names can be specified with a cell array.

Example: select(bag,"Topic",{"/scan","/clock"})

Data Types: char | string | cell

Output Arguments

bagsel — Copy or subset of ros2bag messages

ros2bag object

Copy or subset of ros2bag messages, returned as a ros2bag object.

Version History

Introduced in R2021a