请帮我看看这个程序

hulibo

function [sys,x0,str,ts] = shit(t,x,u,flag,p,omega)
k1=1325200;
m1=3.18;
m2=0.29;
c=62.86;
k2=38000;
switch flag,
  case 0,
    [sys,x0,str,ts]=mdlInitializeSizes;
  case 1,
    sys=mdlDerivatives(t,x,u,p,omega,m1,m2,k2,k1,c);

  case 2,
    sys=mdlUpdate(t,x,u);
  
  case 3,
    sys=mdlOutputs(t,x,u);
  
  case 4,
    sys=mdlGetTimeOfNextVarHit(t,x,u);
  
  case 9,
    sys=mdlTerminate(t,x,u);
  
  otherwise
    error(['Unhandled flag = ',num2str(flag)]);
end
function [sys,x0,str,ts]=mdlInitializeSizes
sizes = simsizes;
sizes.NumContStates  = 4;
sizes.NumDiscStates  = 0;
sizes.NumOutputs     = 1;
sizes.NumInputs      = 0;
sizes.DirFeedthrough = 0;
sizes.NumSampleTimes = 1;   % at least one sample time is needed
sys = simsizes(sizes);

x0  = zeros(4,1);

str = [];

ts  = [0 0];

function sys=mdlDerivatives(t,x,u,p,omega,m1,m2,k2,k1,c)
x1dot=x(2);
x2dot= p*exp(j*t*omega)/m1-c/m1*(x(2)-x(4))-k2*(x(1)-x(3))/m1;
x3dot=x(3);
x4dot=c/m2*(x(2)-x(4))+k2/m2*(x(1)-x(3));
sys=[x1dot,x2dot,x3dot,x4dot]
end

function sys=mdlUpdate(t,x,u)
sys = [];
function sys=mdlOutputs(t,x,u)
sys = x(1);

function sys=mdlGetTimeOfNextVarHit(t,x,u)
sampleTime = 1;    %  Example, set the next hit to be one second later.
sys = t + sampleTime;

function sys=mdlTerminate(t,x,u)
sys = [];
% end mdlTerminate
end



利用这个模型仿真后出现State derivatives returned by S-function 'shit' in block 'shit1/S-Function' during flag=1 call must be a real vector of length 4这样的错误，请大家看看怎么改啊？

cdwxg

p*exp(j*t*omega)/m1-c/m1*(x(2)-x(4))-k2*(x(1)-x(3))/m1;
这个地方不是实向量.