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Get normalizer from function approximator object

Since R2024a



    normalizers = getNormalizer(fcnAppx) returns the normalizer object used by the function approximator object fcnAppx (typically an actor or critic).


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    This example shows how to assign normalizer objects to the actor and critics of a DDPG agent.

    Create DDPG Agent and Extract Actor and Critic

    Create specification objects to define observation and action channels. For this example, the agent has two observation channels. The first channel has a vector with three elements and the second channel has a vector with four elements.

    The action channel carries a two-dimensional vector.

    obsInfo = [rlNumericSpec([3,1]) rlNumericSpec([4,1])];
    actInfo = rlNumericSpec([2,1]);

    Create a default DDPG agent.

    agent = rlDDPGAgent(obsInfo, actInfo);

    Extract the approximator objects.

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

    Create Normalizer Objects

    Create one normalizer object for each input channel. DDPG agents use a Q-value function critic, which requires both the observation and the action as inputs. The Mean, StandardDeviation, Min, and Max properties apply to each element of the channel.

    Create the normalizer for the first observation channel.

    obs1Nrz = rlNormalizer(obsInfo(1).Dimension, ...
        Normalization="zscore", Mean=2, StandardDeviation=3)
    obs1Nrz = 
      rlNormalizer with properties:
            Normalization: "zscore"
                     Mean: 2
        StandardDeviation: 3

    Create the normalizer for the second observation channel.

    obs2Nrz = rlNormalizer(obsInfo(2).Dimension, ...
        Normalization="zerocenter", Mean=4)
    obs2Nrz = 
      rlNormalizer with properties:
        Normalization: "zerocenter"
                 Mean: 4

    Create the normalizer for the action input channel of the Q-value function critic.

    actInNrz = rlNormalizer(actInfo.Dimension, ...
        Normalization="rescale-symmetric", Min=-2, Max=2)
    actInNrz = 
      rlNormalizer with properties:
        Normalization: "rescale-symmetric"
                  Min: -2
                  Max: 2

    To check how the normalizer works on an input, use normalize.

    ans = 2

    Assign Normalizer Objects to Actor and Critic

    To assign new normalizers to the actor and critic, use setNormalizer.

    actor = setNormalizer(actor, [obs1Nrz, obs2Nrz]);
    critic = setNormalizer(critic, [obs1Nrz, obs2Nrz, actInNrz]);

    You can also assign normalizers to selected channels only. For example, to assign normalizers only to the first observation channel (in the order specified by obsInfo) and the action channel, use an indices vector.

    critic = setNormalizer(critic, [obs1Nrz actInNrz], [1 3]);

    Display the normalization properties of the actor and critic.

    ans = 1×2 string
        "zscore"    "zerocenter"
    ans = 1×3 string
        "zscore"    "zerocenter"    "rescale-symmetric"

    Assign Actor and Critic to Agent

    To assign the new actor and critic to the agent, use setActor and setCritic.

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

    To check that agent works, use getAction.

    a = getAction(agent, { ...
        rand(obsInfo(1).Dimension) ...
    ans = 2×1

    Create DQN Agent and Extract Critic

    Define a mixed observation space and a discrete action channel.

    obsInfo = [rlNumericSpec([3,1]), rlFiniteSetSpec([5,3,4,2])];
    actInfo = rlFiniteSetSpec([-1,0,1]);

    Create a default DQN agent.

    agent = rlDQNAgent(obsInfo, actInfo);

    Extract the agent critic.

    critic = getCritic(agent);

    Extract Normalizer Objects from Actor or Critic

    Use getNormalizer to extract an array of normalizer objects from the agent critic.

    crtNrz = getNormalizer(critic)
    crtNrz = 
      1×2 rlNormalizer array with properties:

    Modify Normalizer Objects Using Dot Notation

    Use dot notation to access and change the property of the second normalizer object (associated with the second observation channel).


    Assign the modified normalizer to the critic and assign the critic to the agent.

    critic = setNormalizer(critic, crtNrz);
    setCritic(agent, critic);

    To check that the agent works, use getAction.

    a = getAction(agent, { ...
        rand(obsInfo(1).Dimension) ...
    ans = 0

    Input Arguments

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    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));

    Output Arguments

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    Normalizer objects, specified as an rlNormalizer object or an array of rlNormalizer objects.

    Version History

    Introduced in R2024a