I dont understand the vectors and element parts.

this is the code ( want to plot graph of nonlinear ode)

syms S E I R N a b c d e g h j;
a=0.01;b=0.25;c=0.1;d=0.2;e=0.2;N=520;j=0.167;g=0.8;h=0.02;
f=@(t,y)[((b*N)-(g*y(1))-(j*y(1))-((a*y(1)*y(3))/N)-d*y(1));(j*y*(1)+((a*y(1)*y(3))/N)-(c*y(2))-(d*y(2)));((c*y(2))-(d*y(3))-(h*y(3))-(e*y(3)));((g*y(1))+(e*y(3))-(d*y(4)))];
tspan=[0,100];
xinit=[300 100 75 45];
figure(1)
xlabel('time(years)')
ylabel('population')
ode45(f,tspan,xinit)
legend('S','E','I','R')

this is the error

Error using odearguments (line 95)
@(T,Y)[((B*N)-(G*Y(1))-(J*Y(1))-((A*Y(1)*Y(3))/N)-D*Y(1));(J*Y*(1)+((A*Y(1)*Y(3))/N)-(C*Y(2))-(D*Y(2)));((C*Y(2))-(D*Y(3))-(H*Y(3))-(E*Y(3)));((G*Y(1))+(E*Y(3))-(D*Y(4)))] returns a
vector of length 7, but the length of initial conditions vector is 4. The vector returned by
@(T,Y)[((B*N)-(G*Y(1))-(J*Y(1))-((A*Y(1)*Y(3))/N)-D*Y(1));(J*Y*(1)+((A*Y(1)*Y(3))/N)-(C*Y(2))-(D*Y(2)));((C*Y(2))-(D*Y(3))-(H*Y(3))-(E*Y(3)));((G*Y(1))+(E*Y(3))-(D*Y(4)))] and the
initial conditions vector must have the same number of elements.

Error in ode45 (line 115)
  odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in ttvmd (line 9)
ode45(f,tspan,xinit)

Please help me.......

Answer 1

[James Tursa]

Typo. This

j*y*(1)  <-- Uses the full vector y times the scalar 1

should be this

j*y(1)  <-- Uses only the y(1) element