Main Content


Set approximation model in function approximator object

Since R2020b



    newFcnAppx = setModel(fcnAppx,model) returns a new function approximator object, newFcnAppx, with the same configuration as the original object, fcnAppx, but with the approximation model specified in model.


    collapse all

    Create an environment with a continuous action space and obtain its observation and action specifications. For this example, load the environment used in the example Compare DDPG Agent to LQR Controller.

    Load the predefined environment.

    env = rlPredefinedEnv("DoubleIntegrator-Continuous");

    Obtain observation and action specifications.

    obsInfo = getObservationInfo(env);
    actInfo = getActionInfo(env);

    Create a PPO agent from the environment observation and action specifications. This agent uses default deep neural networks for its actor and critic.

    agent = rlPPOAgent(obsInfo,actInfo);

    To modify the deep neural networks within a reinforcement learning agent, you must first extract the actor and critic function approximators.

    actor = getActor(agent);
    critic = getCritic(agent);

    Extract the deep neural networks from both the actor and critic function approximators.

    actorNet = getModel(actor);
    criticNet = getModel(critic);

    Plot the actor network.


    To validate a network, use analyzeNetwork. For example, validate the critic network.


    You can modify the actor and critic networks and save them back to the agent. To modify the networks, you can use the Deep Network Designer app. To open the app for each network, use the following commands.


    In Deep Network Designer, modify the networks. For example, you can add additional layers to your network. When you modify the networks, do not change the input and output layers of the networks returned by getModel. For more information on building networks, see Build Networks with Deep Network Designer.

    To validate the modified network in Deep Network Designer, you must click on Analyze, under the Analysis section. To export the modified network structures to the MATLAB® workspace, generate code for creating the new networks and run this code from the command line. Do not use the exporting option in Deep Network Designer. For an example that shows how to generate and run code, see Create DQN Agent Using Deep Network Designer and Train Using Image Observations.

    For this example, the code for creating the modified actor and critic networks is in the createModifiedNetworks helper script.


    Each of the modified networks includes an additional fullyConnectedLayer and reluLayer in their main common path. Plot the modified actor network.


    After exporting the networks, insert the networks into the actor and critic function approximators.

    actor = setModel(actor,modifiedActorNet);
    critic = setModel(critic,modifiedCriticNet);

    Finally, insert the modified actor and critic function approximators into the actor and critic objects.

    agent = setActor(agent,actor);
    agent = setCritic(agent,critic);

    Input Arguments

    collapse all

    Function approximator, specified as one of the following:

    To create an actor or critic function object, use one of the following methods.

    • Create a function object directly.

    • Obtain the existing critic from an agent using getCritic.

    • Obtain the existing actor from an agent using getActor.


    For agents with more than one critic, such as TD3 and SAC agents, you must call getModel for each critic representation individually. You cannot call getModel for the array returned by getCritic.

    critics = getCritic(myTD3Agent);
    criticNet1 = getModel(critics(1));
    criticNet2 = getModel(critics(2));

    Function approximation model, specified as one of the following:

    • Deep neural network defined as an array of Layer objects, a layerGraph object, a DAGNetwork object, or a dlnetwork object. The input and output layers of model must have the same names and dimensions as the network returned by getModel for the same function object. Here, the output layer is the layer immediately before the output loss layer.

    • rlTable object with the same dimensions as the table model defined in newRep.

    • 1-by-2 cell array that contains the function handle for a custom basis function and the basis function parameters.

    When specifying a new model, you must use the same type of model as the one already defined in newRep.


    For agents with more than one critic, such as TD3 and SAC agents, you must call setModel for each critic representation individually, rather than calling setModel for the array of returned by getCritic.

    critics = getCritic(myTD3Agent);
    % Modify critic networks.
    critics(1) = setModel(critics(1),criticNet1);
    critics(2) = setModel(critics(2),criticNet2);
    myTD3Agent = setCritic(myTD3Agent,critics);

    Output Arguments

    collapse all

    New function approximator, returned as an object of the same type as oldFcnAppx. Except for its new function approximation model, newFcnAppx is the same as oldFcnAppx.

    Version History

    Introduced in R2020b

    expand all