matlab ode23函数出错

Question

本人MATLAB小白，求助微分方程求解：
函数定义：
function yp = ftest421(x,y)
yp=x.^2./y-x.*cos(y);

执行出错：
>> [x,y]=ode23('ftest421',0,4,1)
Error using odearguments (line 81)
The last entry in tspan must be different from the first entry.

Error in ode23 (line 113)
[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...

>> [x,y]=ode23('ftest421',0,4,1)
Error using odearguments (line 81)
The last entry in tspan must be different from the first entry.

Error in ode23 (line 113)
[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...

求解答！

Answer 1

改为 [x,y]=ode23(@ftest421,[0 4],1)
望采纳追问

依旧不行

追答

你的ftest421.m放在当前工作目录了么？