%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%。function dxdt=zhidao_rk4_5(t，x)。global a b c d r。x1=x(1)。x2=x(2)。x3=x(3)。x4=x(4)。dxdt=[；a*(x2-x1)+x4。d*x1-x1*x3+c*x2。x1*x2-b*x3。x2*x3+r*x4。]。%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%。保存文件，并将其命名为zhidao_rk4_5.m。接着，在命令窗口中输入以下内容设置参数。global a b c d r。a=1。b=2。c=3。d=4。r=5。t_end=10。x0=[1；1；1；1]。