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_HRF3.m
    path of file: ./repos/PsPM/src/ext/VBA/subfunctions
    
    the code of the file until where you have to start completion: function [fx,dfdx,dfdp] = f_HRF3(Xt,P,ut,in)
% Balloon (HRF) model evolution function in log-space
% function [fx,dfdx,dfdp] = f_HRF2(Xt,P,ut,in)
% This function evaluates the evolution function derived from the balloon
% model for the hemodynamic response function. It can be called in two
% ways: (i) as a "stand-alone" evolution function, whereby the system's
% states are hemodynamic states of the balloon model, or (ii) as a
% generalized observation function, where the real system's states are the
% neuronal states of a DCM for fMRI model. Note that the hemodynamic states
% are in log-space, for positivity constrints.

    
function [fx,dfdx,dfdp] = f_HRF3(Xt,P,ut,in)
% Balloon (HRF) model evolution function in log-space
% function [fx,dfdx,dfdp] = f_HRF2(Xt,P,ut,in)
% This function evaluates the evolution function derived from the balloon
% model for the hemodynamic response function. It can be called in two
% ways: (i) as a "stand-alone" evolution function, whereby the system's
% states are hemodynamic states of the balloon model, or (ii) as a
% generalized observation function, where the real system's states are the
% neuronal states of a DCM for fMRI model. Note that the hemodynamic states
% are in log-space, for positivity constrints.


deltat = in.deltat;
n = size(Xt,1);

% Get parameters
[E0,V0,tau0,kaf,kas,epsilon,alpha] = BOLD_parameters;
nreg = numel(in.n5); %n./5;
ind1 = in.ind1;
ind2 = in.ind2;
ind3 = in.ind3;
ind4 = in.ind4;
n1 = in.n1;
n2 = in.n2;
n3 = in.n3;
n4 = in.n4;
n5 = in.n5;
epsilon = 1;
alpha = alpha.*exp(P(in.ind5));

E0 = 1./(1+exp(-(P(ind1)-0.6633)));
dsdp = E0.*(1-E0);
tau0 = tau0.*exp(P(ind2));
kaf = kaf.*exp(P(ind3));
kas = kas.*exp(P(ind4));

% hemodynamic states ...
if in.linearized
    x1 = zeros(nreg,1);
    x2 = ones(nreg,1);
    x3 = ones(nreg,1);
    x4 = ones(nreg,1);
else
    % vasodilatory signal s(t)
    x1 = Xt(n1,:);
    % blood inflow f(t)
    if ~in.logx2
        x2 = Xt(n2,:) + 1; % deviation to steady-state!
    else
        x2 = exp(Xt(n2,:)) + in.xshift;
    end