ParameterTree

Access ROS parameter server

Description

A ParameterTree object communicates with the ROS parameter server. The ROS parameter server can store strings, integers, doubles, Booleans, and cell arrays. The parameters are accessible globally over the ROS network. You can use these parameters to store static data such as configuration parameters.

To directly set, get, or access ROS parameters without creating a ParameterTree object, see rosparam.

The following ROS data types are supported as values of parameters. For each ROS data type, the corresponding MATLAB^® data type is also listed.

ROS Data Type	MATLAB Data Type
32-bit integer	int32
boolean	logical
double	double
string	character vector (char)
list	cell array (cell)
dictionary	structure (struct)

Creation

Syntax

ptree = rosparam

ptree = ros.ParameterTree(node)

Description

ptree = rosparam creates a parameter tree object, ptree. After ptree is created, the connection to the parameter server remains persistent until the object is deleted or the ROS master becomes unavailable.

ptree = ros.ParameterTree(node) returns a ParameterTree object to communicate with the ROS parameter server. The parameter tree attaches to the ROS node, node. To connect to the global node, specify node as [].

Properties

AvailableParameters — List of parameter names on the server

cell array

This property is read-only.

List of parameter names on the server, specified as a cell array.

Example: {'/myParam';'/robotSize';'/hostname'}

Data Types: cell

Object Functions

get	Get ROS parameter value
has	Check if ROS parameter name exists
search	Search ROS network for parameter names
set	Set value of ROS parameter or add new parameter
del	Delete a ROS parameter

Examples

Create ROS ParameterTree Object and Modify Parameters

Start the ROS master and create a ROS node.

master = ros.Core;

Launching ROS Core...
Done in 0.54629 seconds.

node = ros.Node('/test1');

Create the parameter tree object.

ptree = ros.ParameterTree(node);

Set multiple parameters.

set(ptree,'DoubleParam',1.0)
set(ptree,'CharParam','test')
set(ptree,'CellParam',{{'test'},{1,2}});

View the available parameters.

parameters = ptree.AvailableParameters

parameters = 3x1 cell
    {'/CellParam'  }
    {'/CharParam'  }
    {'/DoubleParam'}

Get a parameter value.

data = get(ptree,'CellParam')

data=1×2 cell array
    {1x1 cell}    {1x2 cell}

Search for a parameter name.

search(ptree,'char')

ans = 1x1 cell array
    {'/CharParam'}

Delete the parameter tree and ROS node. Shut down the ROS master.

clear('ptree','node')
clear('master')

Set A Dictionary Of Parameter Values

Use structures to specify a dictionary of ROS parameters under a specific namespace.

Connect to a ROS network.

rosinit

Launching ROS Core...
Done in 0.66963 seconds.
Initializing ROS master on http://172.30.144.24:59754.
Initializing global node /matlab_global_node_57799 with NodeURI http://dcc796195glnxa64:46883/ and MasterURI http://localhost:59754.

Create a dictionary of parameter values. This dictionary contains the information relevant to an image. Display the structure to verify values.

image = imread('peppers.png');

pval.ImageWidth = size(image,1);
pval.ImageHeight = size(image,2);
pval.ImageTitle = 'peppers.png';
disp(pval)

     ImageWidth: 384
    ImageHeight: 512
     ImageTitle: 'peppers.png'

Set the dictionary of values using the desired namespace.

rosparam('set','ImageParam',pval)

Get the parameters using the namespace. Verify the parameter values.

pval2 = rosparam('get','ImageParam')

pval2 = struct with fields:
    ImageHeight: 512
     ImageTitle: 'peppers.png'
     ImageWidth: 384

Shut down ROS network.

rosshutdown

Shutting down global node /matlab_global_node_57799 with NodeURI http://dcc796195glnxa64:46883/ and MasterURI http://localhost:59754.
Shutting down ROS master on http://172.30.144.24:59754.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• Code generation is supported for global node but not for Node since a node cannot create another node in code generation.

Version History

Introduced in R2019b