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Fix topic statistics tutorial for Kilted (backport #5495) #5513

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May 19, 2025
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Fix topic statistics tutorial for Kilted (backport #5495) #5513

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22 changes: 9 additions & 13 deletions source/Tutorials/Advanced/Topic-Statistics-Tutorial/Topic-Statistics-Tutorial.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ Enabling topic statistics (C++)
Background
----------

This is a short tutorial on how to enable topic statistics in ROS 2 and view the published statistics output using command line tools (:doc:`ros2topic <../../Beginner-CLI-Tools/Understanding-ROS2-Topics/Understanding-ROS2-Topics>`).
This is a short tutorial on how to enable topic statistics in ROS 2 and view the published statistics output using command line tools (:doc:`ros2 topic <../../Beginner-CLI-Tools/Understanding-ROS2-Topics/Understanding-ROS2-Topics>`).

ROS 2 provides the integrated measurement of statistics for messages received by any subscription,
called Topic Statistics.
Expand Down Expand Up @@ -95,7 +95,7 @@ Open the file using your preferred text editor.
// configure the topic name (default '/statistics')
// options.topic_stats_options.publish_topic = "/topic_statistics"

auto callback = [this](std_msgs::msg::String::SharedPtr msg) {
auto callback = [this](const std_msgs::msg::String & msg) {
this->topic_callback(msg);
};

Expand All @@ -104,9 +104,9 @@ Open the file using your preferred text editor.
}

private:
void topic_callback(const std_msgs::msg::String::ConstSharedPtr msg) const
void topic_callback(const std_msgs::msg::String & msg) const
{
RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg->data.c_str());
RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg.data.c_str());
}
rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription_;
};
Expand Down Expand Up @@ -253,15 +253,15 @@ The terminal should start publishing statistics messages every 10 seconds, becau
nanosec: 930797670
statistics:
- data_type: 1
data: .nan
data: 0.5522003000000001
- data_type: 3
data: .nan
data: 0.756992
- data_type: 2
data: .nan
data: 0.269039
- data_type: 5
data: 0.0
data: 20.0
- data_type: 4
data: .nan
data: 0.16441001797065166
---
measurement_source_name: minimal_subscriber_with_topic_statistics
metrics_source: message_period
Expand Down Expand Up @@ -300,10 +300,6 @@ data_type value statistics

Here we see the two currently possible calculated statistics for the ``std_msgs::msg::String`` message published
to ``/topic`` by the ``minimal_publisher``.
Because the ``std_msgs::msg::String`` does not have a message header, the ``message_age`` calculation cannot be performed,
so NaNs are returned.
However, the ``message_period`` can be calculated and we see the statistics populated
in the message above.

Summary
-------
Expand Down