%% Add an Infusion Dose
% This example shows how to add a constant-rate infusion dose to a one-compartment model.
%% Background
% Suppose you have a one-compartment model with a species named drug that represents the total amount of drug in the body. The drug is removed from the body via the first-order elimination represented by the reaction drug -> null, with the elimination rate constant ke. In other words, the drug concentration versus the time profile follows the monoexponential decline {C_t} = {C_0}{e^{ - {k_e}t}}, where C_t is the drug concentration at time t, C_0 is the initial concentration, and ke is the elimination rate constant. This example shows how to set up such a one-compartment model and add an infusion dose at a constant rate of 10 mg/hour for the total dose amount of 250 mg.
%% Create a One-compartment Model
% Create a SimBiology model named onecomp.

m1 = sbiomodel('onecomp');

%
% Define the elimination of the drug from the system by adding a reaction drug -> null to the model.

r1 = addreaction(m1,'drug -> null');

% The species drug is automatically created and added to the compartment. The null species is a reserved species that acts as a sink in this reaction.
%
% Add a mass action kinetic law to the reaction. This kinetic law defines the drug elimination to follow the first-order kinetics.

k1 = addkineticlaw(r1,'MassAction');

%
% Define the elimination rate parameter ke and add it to the kinetic law.

p1 = addparameter(k1,'ke','Value',1.0,'ValueUnits','1/hour');

%
% Specify the rate parameter ke as the forward rate parameter of the reaction by setting the ParameterVariableNames property of kinetic law object k1. This allows SimBiology to determine the reaction rate for drug -> null reaction.

k1.ParameterVariableNames = 'ke';

%
%% Set up an Infusion Dose
% Add a dose object to the model using the adddose method. Specify the amount of the dose (Amount), the dose target (TargetName), and the infusion rate (Rate). You also need to set the Active property of the dose object to true so that the dose is applied to the model during simulation.

d1 = adddose(m1,'InfusionDose');
d1.Amount = 250;
d1.TargetName = 'drug';
d1.Rate = 10;
d1.RateUnits = 'milligram/hour';
d1.Active = true;

%
%% Simulate the Model
% Change the simulation stop time to 48 hours to see the complete time course.

cs = getconfigset(m1);
cs.StopTime = 48;
cs.TimeUnits = 'hour';
sd = sbiosimulate(m1);

%
%% Plot results
% Plot the concentration versus the time profile of the drug in the system.

sbioplot(sd);

% Copyright 2015 The MathWorks, Inc.