Determine the condition to find elements inside semi circular region in a rectangular mesh

4 次查看（过去 30 天）

显示更早的评论

Abhishek Saini 2018-11-6

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/428207-determine-the-condition-to-find-elements-inside-semi-circular-region-in-a-rectangular-mesh

评论： Abhishek Saini 2018-12-4

采纳的回答： KSSV

points.png

在 MATLAB Online 中打开

I have a rectangular mesh of 500000x500000. I extracted the coordinates of the mesh elements. Now I would like to remove elements in the semicircular form from this rectangular mesh. I have the function to remove elements. But I am struggling to set the condition for the semicircular region to determine all the elements inside the semicircular region. For example if ex and ey are the coordinates of elements in mesh, then I am using

find(ex<=R*cos(theta) & ey <=R*sin(theta)).
How to set this condition according to the grid points in the rectangular mesh. I have also attached the image for more clarity.
Thanks.

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。

采纳的回答

KSSV 2018-11-6

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/428207-determine-the-condition-to-find-elements-inside-semi-circular-region-in-a-rectangular-mesh#answer_345395

编辑：KSSV 2018-11-6

在 MATLAB Online 中打开

Read about inpolygon. This should help you.

M = 100 ; 
N = 100 ;
x = linspace(0,1,M) ;
y = linspace(0,1,N) ;
[X,Y] = meshgrid(x,y) ;
% semi circle
O = [0.5  0. ];  % origin of circle 
R = 0.3 ;         % RAdius of circle 
th = linspace(0,2*pi) ;
xc = O(1)+R*cos(th) ; 
yc = O(2)+R*sin(th) ; 
% Get points lying inside circle 
idx = inpolygon(X(:),Y(:),xc,yc) ;
% plot 
figure
hold on
plot(X,Y,'.r') ;
plot(xc,yc,'b')
plot(X(idx),Y(idx),'.k')