error in bvp4c "??? Undefined function or method 'mtimes' for input arguments of type 'struct'.

Hi

I'm solving the following code using bvp4c

function mat4bvpcasympt

 n=100; 
 x=linspace(0,1,n+1); 
f=0.2*x.^2; 
H=1-f; 
S=spline(x,H);
solinit = bvpinit(linspace(0,1,n),@mat4init);
sol = bvp4c(@mat4ode,@mat4bc,solinit,[],S);
xint=linspace(0,1);
phis=real(deval(sol,xint));

%% S is the interpolation function input arguments

function dydx = mat4ode(x,y,S)

dydx =[y(2)

        -exp(-1/2*y(1))*S];

%% And I get the following errors:

??? Undefined function or method 'mtimes' for input arguments of type 'struct'.

Error in ==> mat4bvpcasympt1>mat4ode at 85 dydx =[y(2)

Error in ==> bvparguments at 116 testODE = ode(x1,y1,odeExtras{:});

Error in ==> bvp4c at 130 [n,npar,nregions,atol,rtol,Nmax,xyVectorized,printstats] = ...

Error in ==> mat4bvpcasympt1 at 51 sol = bvp4c(@mat4ode,@mat4bc,solinit,[],S);

Can someone help me to encounter the error? Thanks in advance