Bug fminbnd not working

3 次查看（过去 30 天）
Stephen Wilkerson
Stephen Wilkerson 2019-1-20
编辑： Torsten 2022-7-17
fplot(@(x) x*(sin(x))^2*cos(x),[-2*pi 2*pi]);
[xMin1 fvalmin1] = fminbnd('-x*(sin(x))^2*cos(x)', -6, 6)
returns xMin1 = 1.0954
fvalmin1 = -0.3963
How is this possible, look at the plot?
  3 个评论
显示 1更早的评论
Stephen Wilkerson
Stephen Wilkerson 2019-1-20
Not where the minimum is! look at the plot
Stephen Wilkerson
Stephen Wilkerson 2019-1-20
Solved, The function doesn't really do much, it give you the nearest point that's a minimum to it's starting point. In my case it woud be 0 as the starting point. Typical

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Walter Roberson
Walter Roberson 2019-1-20
No bug. fminbnd is a local minimizer, not a global minimizer.
  3 个评论
显示 1更早的评论
Torsten
Torsten 2022-7-17
编辑：Torsten 2022-7-17
Ran in:
Since the changes in the x-values are in the order of 1e-6, you must choose a smaller value for TolX:
a=-200; b=-979.8997; c=7.1833e+05; d=24.4232;e=-6.6083;
x1=0; x2=4.1135e-06;
f=@(x)a-(a-b)*cos(c*(x-x1)) + d*e*sin(c*(x-x1))
f = function_handle with value:
@(x)a-(a-b)*cos(c*(x-x1))+d*e*sin(c*(x-x1))
fplot(f, [x1 x2])
options = optimset('TolX',1e-8);
[xmin, min]=fminbnd(f, x1, x2, options)
xmin = 2.8422e-07
min = -996.4246
Zhe Yu
Zhe Yu 2022-7-17
Hi Torsten, thank you very much!

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Solver Outputs and Iterative Display 的更多信息

标签

产品


版本

R2018b

Community Treasure Hunt

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

Start Hunting!

Translated by