MATLAB在XY平面中移动点 [英] MATLAB moving a point in the XY plane

问题描述

在MATLAB中，我有一个由有限数量的点表示的XY平面. x的可能值存储在向量X中，y的可能值存储在另一个向量Y中.我有一个点，说A，使得A(1)属于X的x坐标和A(2 )所属的Y是y坐标.

In MATLAB, I have an XY plane that is represented by finite number of points. The possible values of x are stored in a vector X and the possible values of y are stored in another vector Y. I have a point, say A, such that A(1) belongs to X is the x-coordinate and A(2) belongs to Y is the y-coordinate.

如果A点位于中间，则它可以以8种方式之一移动:

This point A can move in one of 8 ways if it is in the middle:

          .   .   .                      .   A                .    .

          .   A   .        OR            .   .       OR       .    A

          .   .   .                                           .     .

当然，如果点A在边上(有时只有5个，如果是角则只有3个)，这些点的集合也会改变.如何找到这些"1跳"相邻点的集合?那套"k-hop"相邻点呢?所谓集合，是指两个向量，一个用于x坐标，另一个用于y坐标.谢谢！

Of course, the set of these points changes if the point A is on the edge (sometimes only 5, sometimes only 3 if it is a corner). How can I find the set of these "1-hop" neighboring points? What about the set of "k-hop" neighboring points? By set I mean two vectors one for x-coordinates and another for y-coordinates. Thanks!

推荐答案

请考虑以下代码:

%# create grid of 2D coordinates
sz = [5 6];
[X,Y] = meshgrid(1:sz(2),1:sz(1));

%# point A
A = [1 2]

%# neighboring points
k = 2;                               %# hop size
[sx,sy] = meshgrid(-k:k,-k:k);       %# steps to get to neighbors
xx = bsxfun(@plus, A(1), sx(:));     %# add shift in x-coords
xx = min(max(xx,1),sz(2));           %# clamp x-coordinates within range
yy = bsxfun(@plus, A(2), sy(:));
yy = min(max(yy,1),sz(1));
B = unique([xx yy],'rows');          %# remove duplicates
B(ismember(B,A,'rows'),:) = [];      %# remove point itself

具有k=2跳的点A = (1,2)的结果:

B =
     1     1
     1     3
     1     4
     2     1
     2     2
     2     3
     2     4
     3     1
     3     2
     3     3
     3     4

和解决方案的说明:

x A x x . .
x x x x . .
x x x x . .
. . . . . .
. . . . . .

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