function f = epi1dae(t,y)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%  function f = epi1dae(t,y)                             %
%  Solution to CSE Your Homework Assignment Project 6    %
%  More Models of Infection: It's Epidemic               %
%  epidae.m Dianne P. O'Leary   11/03                    %
%                                                        %
%  This program evaluates dy/dt for the DAE model of     %
%  Problem 2.                                            %
%  The y vector has 3 components:                        %
%        infected, susceptible, and recovered.           %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

global mytrans myrecov 

inf = y(1);
sus = y(2);
rec = y(3);

f(1,1) =   mytrans*inf*sus - inf/myrecov;
f(2,1) = - mytrans*inf*sus;
f(3,1) =   0;