How to extract points from a 3D plot that fall within a particular distance from the center coordinate?

3 次查看（过去 30 天）
sai sai
sai sai 2021-8-18
评论： sai sai 2021-8-18
Hello, I am a novice in matlab programmming. I am working on a computational project where I have a 3dimensional plot with thousands of points. Now I would like to fix one point having coordinate (x,y,z). At a particular distance r as a cutoff from (x,y,z), I would like to extract all the points in the plot that fall within the distance (or radius) r. I am not sure of how i can use euclidean distance formula for this. Please help me out.
Thanks in advance.

请先登录，再回答此问题。

采纳的回答

Wan Ji
Wan Ji 2021-8-18
编辑：Wan Ji 2021-8-18
If you have Coor is a n by 3 matrix as the coordinates of n points in 3d space and a fixed point (x,y,z). Then the points within the distance r can be obtained by
p = sqrt((Coor(:,1)-x).^2 + (Coor(:,2)-y).^2 + (Coor(:,3)-z).^2)<r;
Coor_withindistance_r = Coor(p,:);
  4 个评论
显示 2更早的评论
Wan Ji
Wan Ji 2021-8-18
编辑：Wan Ji 2021-8-18
function [coor_num, neighbors_with_r] = Coordinates(X,Y,Z,Coor)
r = 1:10;
coor_num = zeros(length(r),1);
neighbors_with_r = cell(length(r),1);
for i = 1:1:length(r)
p = sqrt((Coor(:,1)-X).^2 + (Coor(:,2)-Y).^2 + (Coor(:,3)-Z).^2)<r(i);
Coor_withindistance_r = Coor(p,:);
coor_num(i) = size(Coor_withindistance_r, 1);
neighbors_with_r{i,1} = Coor_withindistance_r;
end
end
This may work, it returns the numbers of coordinates with different distance r (an array), and returns their coordinates. @sai sai

请先登录，再进行评论。

更多回答（1 个）

Turlough Hughes
Turlough Hughes 2021-8-18
编辑：Turlough Hughes 2021-8-18
The points which are within a radius, r, from the origin can be obtained as follows:
index = sum(X.^2,2) < r^2; % X is an n by 3 array of points
Xthresh = X(index,:);
Note, squaring r is more efficient than taking the square root for ALL of the points in X.
For a starting point other than the origin, e.g. p (1 by 3), points in X within a threshold radius r from the point p can be obtained as follows:
index = sum(X.^2 - p,2) < r^2;
Xthresh = X(index,:);

类别

在 Help Center 和 File Exchange 中查找有关 Line Plots 的更多信息

标签

产品


版本

R2021a

Community Treasure Hunt

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

Start Hunting!

Translated by