求助！！！matlab SIR模型function dy=odesir(t,y,beta,gamma)dy=[-beta*y(1)*y(2);beta*y(1)*y(2)-gamma*y(2);gamma*y(2)];N=100;beta=0.01;gamma=0.1;tspan=[0:50];y0=[99,1,0];[t,y]=ode45(@odesir,tspan,y0,[],beta,gamma);plot(t,y);xlabel('time');ylabel('population');legend('S','I','R')end运行不出来，总是提示“输入参数的数目不足出错 odesir (line 2)y=[-beta*y(1)*y(2);beta*y(1)*y(2)-gamma*y(2);gamma*y(2)];"