function cxsj()
 D=input('缸径D=');
 S=input('汽缸行程S=');
n=input('转速=');
epsilon=input('压缩比=');
Ze=input('进气门个数=');
Za=input('排气门个数=');
Po=input('大气压力=');
To=input('大气温度=');
L=input('连杆长度=');
r=input('曲柄半径=');

  for phi=0:1:720
     if phi<180
      Ma = S.*pi.*(D/2)^2.*28.97;   %空气质量
      vf=S.*pi.*D^2./4
     Va = pi^2.*D^2.*S./(8.*180).*(sin(pi.*phi./180)+r./(2.*L).*sin(pi.*2.*phi./180)./(1-(r./L*sin(pi.*phi./180)^0.5)));   %汽缸容积变化率
      
          [x,y] = ode45(@xxx,[0 180],1);
     
        plot(x,vf-y)
        grid
   
      end
  end
  
    % dV/dphi的表达式   
     function Y=xxx(x,y)
     global D S L r
   
     Y=pi^2.*D^2.*S./(8.*180).*(sin(pi.*x./180)+r./(2.*L).*sin(pi.*2.*x./180)./(1-(r./L*sin(pi.*x./180)^0.5)));




运行后出现??? Error using ==> funfun\private\odearguments
Solving XXX requires an initial condition vector of length 0.

Error in ==> ode45 at 173
[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, ...

Error in ==> Untitled8 at 19
          [x,y] = ode45(@xxx,[0 180],1);
到底是怎么回事啊???