MATLAB: Solving DAEs ,errors happen ,i do not know why

Question

code:

 function mainsolve
  M=[1 0 0 0;
     0 1 0 0;
     0 0 0 0;
     0 0 0 0];
  y0=[1;0;1;0];
  tspan=[0,1];
  options = odeset('Mass',M,'RelTol',1e-4,...
                   'AbsTol',[1e-6 1e-6 1e-6,1e-6],...
                   'Vectorized','on');
  [t,y] = ode15s(@ct,tspan,y0,options);
  plot(t,y);
  function dy=ct(r,y)
  dy=[-8*y(1)+8*y(3)+0.2*(1-y(2))*exp(20-20/y(1));
  -8*y(2)+8*y(4)+0.2*(1-y(2))*exp(20-20/y(1));
  -4*y(1)+5*y(3)-0.92;
  -4*y(2)+4*y(4)];

errors message:

 Error using  - 
 Matrix dimensions must agree.
 Error in odenumjac (line 147)
  Fdiff = Fdel - Fvalue(:,ones(1,ny));
 Error in daeic12 (line 37)
  [DfDy,Joptions.fac,nF] = odenumjac(fun, {t0,y,args{:}}, f, Joptions);
 Error in ode15s (line 310)
    [y,yp,f0,dfdy,nFE,nPD,Jfac] = daeic12(odeFcn,odeArgs,t,ICtype,Mt,y,yp0,f0,...
 Error in mainsolve (line 11)
 [t,y] = ode15s(@ct,tspan,y0,options);

Answer 1

Does this work ?

function mainsolve
M=[1 0 0 0
   0 1 0 0
   0 0 0 0
   0 0 0 0];
y0=[1 0 0.984 0];
tspan=[0 1];
options = odeset('Mass',M,'RelTol',1e-4,...
                 'AbsTol',[1e-6 1e-6 1e-6,1e-6],...
                 'Vectorized','on');
[t,y] = ode15s(@ct,tspan,y0,options);
plot(t,y)
function dy=ct(r,y)
dy=[-8*y(1)+8*y(3)+0.2*(1-y(2))*exp(20-20/y(1))
    -8*y(2)+8*y(4)+0.2*(1-y(2))*exp(20-20/y(1))
    -4*y(1)+5*y(3)-0.92
    -4*y(2)+4*y(4)];

Best wishes

Torsten.