说明：  解常微分方程的Matlab程序 字符串ypfun是用以表示f(t, y)的M文件名, tspan=[t0, tfinal]表示自变量初值t0和终值tf y0表示初值向量y0，可选参数options为用odeset设置精度等参数。 输出列向量tout表示节点，输出矩阵yout 表示数值解，每一列对应y的一个分量。若无输出参数，则作出图形。
(Solution of ordinary differential equations of the Matlab program is used to indicate ypfun string f (t, y) M-file name, tspan = [t0, tfinal] said that since the variable t0 initial and final values of tf y0, said initial vector y0 , optional parameters to set options for the use of odeset accuracy and other parameters. The output column vector tout that node, the output matrix yout that of numerical analysis, each column corresponds to y of a component. If there are no output parameters, then make a graph.)