how to plot a fourth ordinary differential equation

Question

Lorenzo Mereu 2021-3-8

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/766301-how-to-plot-a-fourth-ordinary-differential-equation

回答： David Jacob 2021-3-8

Hi, I'm new on matlab and maybe this could be a silly answer. I solved this fourth order differential equation, but I have some problems with the function "fplot(usol(x))". Could anyone help me? Thank you! That's the code:

syms u(x) d

a=0.1

Du=diff(u,x)

D2u=diff(u,x,2)

D3u=diff(u,x,3)

ode=diff(u,x,4)==-4*(a^4)*u

c1=u(0)==d

c2=D2u(0)==0

c3=D2u(1)==0

c4=D3u(1)==0

conds=[c1 c2 c3 c4]

usol(x)=dsolve(ode,conds)

usol(x)=subs(usol(x))

fplot(usol(x));

-------------------------------

I report also the error:

Error using fplot>singleFplot (line 240)

Input must be a function or functions of a single

variable.

Error in

fplot>@(f)singleFplot(cax,{f},limits,extraOpts,args)

(line 200)

hObj = cellfun(@(f)

singleFplot(cax,{f},limits,extraOpts,args),fn{1},'UniformOutput',false);

Error in fplot>vectorizeFplot (line 200)

hObj = cellfun(@(f)

singleFplot(cax,{f},limits,extraOpts,args),fn{1},'UniformOutput',false);

Error in fplot (line 166)

hObj =

vectorizeFplot(cax,fn,limits,extraOpts,args);

Error in fourhordertravesuoloelastico (line 18)

fplot(usol(x));

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

David Jacob 2021-3-8

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/766301-how-to-plot-a-fourth-ordinary-differential-equation#answer_642221

The line usol(x) = subs(usol(x)) isn't doing anything. The function fplot can't plot your function your function, because it is dependent on x and d. Give d a value and it will work. Put something like: subs(usol,d,value)