how can I find the radius of part of spherical surface

Question

israel gabay 2017-12-19

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/373675-how-can-i-find-the-radius-of-part-of-spherical-surface

评论： israel gabay 2017-12-20

I had an experiment that gave my part of spherical surface.

I didnt know where the (x,y,z) location of the surface and is radius? I want to find a way to determine the radius, and if there is some fit for spherical surface it will be the best option.

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

Torsten 2017-12-19

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/373675-how-can-i-find-the-radius-of-part-of-spherical-surface#answer_296905

编辑：Torsten 2017-12-19

Use fminsearch to determine radius and center of the sphere which approximates your point cloud best (4 unknowns).

To this end, you will need to project your points onto the surface of a sphere suggested by fminsearch, calculate the distances between your points and their projections and sum them up. This will give you the function to minimize.

Best wishes

Torsten.

2 个评论
显示无隐藏无

Torsten 2017-12-19

Im not sure how to use fminsearch,

I have x y z there are my data (each of them are vector with n values) and the function I want to check is (x-x0)^2+(y-y0)^2+(z-z0)^2-R^2=0

but I dont understand how to use fmin for that

thanks a lot! Israel.

Torsten 2017-12-19

During the optimization process, fminsearch gives you 4 parameters: x0, y0, z0 and R.

With these parameters you will have to calculate the distances d_i of all your points (x_i,y_i,z_i) (i=1,...,N) from the sphere (x-x0)^2+(y-y0)^2+(z-z0)^2 = R^2.

The return parameter to fminsearch is then sum_{i=1}^{N} d_i, and fminsearch will try to minimize this sum.

Best wishes

Torsten.

请先登录，再进行评论。

Answer 2

israel gabay 2017-12-19

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/373675-how-can-i-find-the-radius-of-part-of-spherical-surface#answer_296923

I still dont understand how to find with fmin the parameter (x0,y0,z0,R)

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Torsten 2017-12-19

You don't need to find them, fminsearch will do.

You only have to provide a starting guess for x0,y0,z0 and R.

Best wishes

Torsten.

请先登录，再进行评论。

Answer 3

israel gabay 2017-12-19

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/373675-how-can-i-find-the-radius-of-part-of-spherical-surface#answer_296926

its good that fmin will find them but how I use this function I dont find the write syntax u can write please how I need to use this function exactly

Thanks again !

3 个评论
显示 1更早的评论隐藏 1更早的评论

Torsten 2017-12-19

This might be of help if the use of fminsearch is too difficult:

https://de.mathworks.com/help/vision/ref/pcfitsphere.html

Best wishes

Torsten.

israel gabay 2017-12-20

Thanks!

I will try to use the 2 option.

请先登录，再进行评论。

how can I find the radius of part of spherical surface

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

回答（3 个）

2 个评论
显示无隐藏无

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

3 个评论
显示 1更早的评论隐藏 1更早的评论

另请参阅

类别

标签

Community Treasure Hunt

how can I find the radius of part of spherical surface

0 个评论 显示 -2更早的评论隐藏 -2更早的评论

回答（3 个）

2 个评论 显示 无隐藏 无

1 个评论 显示 -1更早的评论隐藏 -1更早的评论

3 个评论 显示 1更早的评论隐藏 1更早的评论

另请参阅

类别

标签

Community Treasure Hunt

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

2 个评论
显示无隐藏无

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

3 个评论
显示 1更早的评论隐藏 1更早的评论