How is f(x) evaluated for each iteration using fsolve?

9 次查看（过去 30 天）
TS
TS 2019-1-14
评论： Torsten 2019-1-15
I'm using fsolve for an unconstrained non-linear function. And I notice that fval is much different than f(x) for the last iteration. How exactly is f(x) calculated?
  13 个评论
显示 11更早的评论
TS
TS 2019-1-14
So it's the squared error? I got confused because it says f(x) even though it's the sum of squared function values.
Thanks so much!
Stephen23
Stephen23 2019-1-14
编辑：Stephen23 2019-1-14
"I got confused because it says f(x) even though it's the sum of squared function values."
I agree that the inconsistent labeling is confusing at best, and at worst incorrect. You should make a bug report (and include a link to this thread).

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Martijn
Martijn 2019-1-15
The values shown under f(x) in the iteration table are indeed not literally the function values at that given iteration, you are seeing the square of the norm of the function value vector here; as documented, see:
http://www.mathworks.com/help/releases/R2018a/optim/ug/iterative-display.html#f89451
The reason for this is that "fsolve" can actually solve whole systems of equations where f(x) would then be a whole vector of values. Displaying this whole vector in the table is not really feasible, there is not enough space for that. Hence, instead, a measure is shown which basically summarizes the whole f(x) vector in a single measure which also actually is representative for how good the current solution is.
We could look into whether we can perhaps change the header to ||f(x)||^2 in future releases to better illustrate this.

更多回答（1 个）

RANJEET YADAV
RANJEET YADAV 2019-1-14
f(x)=fsolve(@(x) funname(x),x=1);

类别

在 Help Center 和 File Exchange 中查找有关 Surrogate Optimization 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