Error using feval and in odearguments?

I'm trying to simulate the SEIR model for dengue fever using the following differential equations:

function ypseir =ypseir(t,y)
u=0.0045
N=5535002
S=5535002
E=50
I=50
J=0
R=0
v=0.0045
B=0.375
o=1/8.5
z=1/6
ypseir(1) = u*N-((B*(J/N))+u)*S
ypseir(2) = ((B *(J/N))*S)-(u+o)*E
ypseir(3) = o*E+(u+z)*I
ypseir(4) = z*I-u*R
ypseir = [ypseir(1) ypseir(2) ypseir(3) ypseir(4)]';
to = 0;
tf =100;
yo = [5535002 50 50 0];
[t y] = ode45('ypseir',[to tf],yo);
plot(t,y(:,1),t,y(:,2),t,y(:,3),y(:,4))
title('Human Population Without Control')
xlabel('time')
ylabel('susceptible, exposed, infected, recovered')

And I'm presented with the following errors:

Error using feval Maximum recursion limit of 500 reached.
Error in odearguments (line 87) f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Truthfully I'm unsure how to use MATLAB and compute the SEIR model. Help is needed! Thank you!

Answer 1

[Walter Roberson]

Store the below in ypseir_driver.m

function ypseir_driver

    to = 0;
    tf =100;
    yo = [5535002 50 50 0];
    [t y] = ode45(@ypseir,[to tf],yo);
    plot(t, y(:,1), 'c', t, y(:,2), 'y', t, y(:,3), 'r', t, y(:,4), 'b')
    title('Human Population Without Control')
    xlabel('time')
    ylabel('susceptible, exposed, infected, recovered')
    legend('susceptible', 'exposed', 'infected', 'recovered');

function dy = ypseir(t,y)

    u = 0.0045;
    N = 5535002;
    S = 5535002;
    E = 50;
    I = 50;
    J = 0;
    R = 0;
    v = 0.0045;
    B = 0.375;
    o = 1/8.5;
    z = 1/6;
    dy(1,1) = u*N-((B*(J/N))+u)*S;
    dy(2,1) = ((B *(J/N))*S)-(u+o)*E;
    dy(3,1) = o*E+(u+z)*I;
    dy(4,1) = z*I-u*R;

[Muse Riveria]

Hi! Thank you for your answer, despite following your instructions (whilst the error did disappear), when I "ran" the functions no graph was computed.