Problem with fsolve -- Failure in initial user-supplied objective function evaluation

10 次查看（过去 30 天）
Paladin
Paladin 2014-7-22
评论： Paladin 2014-7-24
I am not sure whether it is due to the problem fsolve cannot solve this equation:
f=[(log(1+2*d)/2*d)-q];
What I did was, first of all I made a m file like this:
function f=sr(d)
f=[(log(1+2*d)/2*d)-q];
I have a series of q values, so in my main function I wrote this:
D=zeros(184,1);
c0=[0 4];
for i=1:184;
q=Q(i,1);
D(i,1)=fsolve(@sr,c0);
end
where Q stores the values for q.
The I encountered error messages as below:
??? Error using ==> mtimes
Inner matrix dimensions must agree.
Error in ==> sr at 2
f=[(log(1+2*d)/2*d)-0.715667311];
Error in ==> fsolve at 248
fuser = feval(funfcn{3},x,varargin{:});
Caused by:
Failure in initial user-supplied objective function evaluation. FSOLVE
cannot continue.
Is there anything I did wrong? Or is there any way I can solve this equation?
Many thanks for helping hands in advance.

请先登录，再回答此问题。

采纳的回答

Matt J
Matt J 2014-7-22
编辑：Matt J 2014-7-22
c0 should be a scalar. Since you only have 1 equation, you presumably only have 1 unknown. So, if d is a scalar, its initial guess c0 should be a scalar, too.
You also haven't passed q to sr() in any way. See here for ways to pass fixed parameters to obejctive functions,
http://www.mathworks.com/help/optim/ug/passing-extra-parameters.html

更多回答（1 个）

Michael Haderlein
Michael Haderlein 2014-7-22
Actually, I'm a bit puzzled why that specific error appears. However, a few questions arise:
(I): Why is there no input variable q in the function sr? It is used in the function. Did you maybe use global variables?
(II): Why do you use the [] brackets in sr?
(III): If you set d to a vector ([0 4] in your example), you most likely want to get sf(0) and sf(4)? Then you need to use element-wise operations in your function (.* instead of *).
(IV): If you really want to solve sr simultaneously from two different starting points, you will get two answers. Accordingly, D needs to have two columns.
Hope I could help you. Best regards,
Michael
  1 个评论
Paladin
Paladin 2014-7-24
I am a newbie and just followed the tutorial videos on youtube, and obviously I have misunderstood some of the examples. Thank you for asking these questions so I can have a better understanding of these examples :-)

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Get Started with Optimization Toolbox 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by