You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: f_Qlearn_dynLR.m
    path of file: ./repos/VBA-toolbox/demos/_models
    
    the code of the file until where you have to start completion: function  [fx,dfdx] = f_Qlearn_dynLR(x,P,u,in)
% evolution function of q-values of a RL agent with dynamic learning rate
% [fx] = f_Qlearn_dynLR(x,P,u,in)
% Here, there are only two q-values to evolve, i.e. there are only two
% actions to reinforce (2-armed bandit problem).
% IN:
%   - x_t : q-values and learning rate
%   - P : [useless]

    
function  [fx,dfdx] = f_Qlearn_dynLR(x,P,u,in)
% evolution function of q-values of a RL agent with dynamic learning rate
% [fx] = f_Qlearn_dynLR(x,P,u,in)
% Here, there are only two q-values to evolve, i.e. there are only two
% actions to reinforce (2-armed bandit problem).
% IN:
%   - x_t : q-values and learning rate
%   - P : [useless]
%   - u : u(1)=previous action, u(2)=feedback
%   - in : [useless]
% OUT:
%   - fx: evolved q-values and learning rate (3x1)

alpha = 1./(1+exp(-x(3))); % learning rate is bounded between 0 and 1.
r = u(2);
fx = x;

% index of Qvalue to update
if u(1)==1
    a = 1;
else
    a = 2;
end