Gradient in RL DDPG Agent

Where can I find the function description for the gradient while finding the critic gradient or the actor gradient used in RL DDPG agent? When I open gradient by right clicking on it , I get the Numerical gradient help file, Is this the correct one? What does the text 'output-input' mean when the dQdInput is taken in the next line of the code.

I want to use the gradient function for my custom agent.

            criticGradient = gradient(this.Critic,'loss-parameters',...
                    [Observations, Actions], targetq);
            dQdInput=gradient(obj.Critic,'output-input',[Observations,Actions]);

Answer 1

[Emmanouil Tzorakoleftherakis]

If you put a break point right before 'gradient' is called in this example, you can step in and see the function implementation. This method is not 'public', that's why there is no formal doc page, but you can see the description below.

Hope that helps