How to determine what grid cell a given point is in?

Question

Darcy 2015-7-16

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/230152-how-to-determine-what-grid-cell-a-given-point-is-in

评论： Samson Williams 2021-9-30

I apologize if this question has been asked before but I have looked and cannot find an answer.

Lets say I have a grid with x-vector [1:10] and y-vector [1:10]. And now I have the point (3.994, 7.554).

Is there an easy way to determine which grid cell this point lies in? I am currently solving the problem with for loops to find the nearest x- and y-line to the point. But I am sure there is an embedded function which addresses the problem.

Any help is appreciated. Cheers

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Azzi Abdelmalek 2015-7-16

What is the expected result for this case?

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Star Strider 2015-7-16

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/230152-how-to-determine-what-grid-cell-a-given-point-is-in#answer_186302

在 MATLAB Online 中打开

One possibility:

x_vector = [1:10];
y_vector = [1:10];
point = [3.994, 7.554];
x_grid = find(x_vector <= point(1), 1, 'last');
y_grid = find(y_vector <= point(2), 1, 'last');
x_grid = [x_grid x_grid+1]
y_grid = [y_grid y_grid+1]

The output are the final values of ‘x_grid’ and ‘y_grid’

4 个评论
显示 2更早的评论隐藏 2更早的评论

Mateus Mengatto 2021-3-9

Perfect! Thanks

Star Strider 2021-3-9

Mateus Mengatto — My pleasure!

请先登录，再进行评论。

Answer 2

Azzi Abdelmalek 2015-7-16

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/230152-how-to-determine-what-grid-cell-a-given-point-is-in#answer_186303

在 MATLAB Online 中打开

You can use

[xx,yy]=meshgrid(x,y)

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Samson Williams 2021-9-30

Can you please elaborate on this answer? It is too vague to understand what you mean.

请先登录，再进行评论。

Answer 3

Walter Roberson 2015-7-16

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/230152-how-to-determine-what-grid-cell-a-given-point-is-in#answer_186310

在 MATLAB Online 中打开

For values no smaller than 1:

[floor(x), floor(y)]

More generally,

[~, binx] = histc(x, [x_values(:); inf]);
[~, biny] = histc(y, [y_values(:); inf]);

this assumes that values might be greater than x_values(end) -- for example with x_values = 1:10 then this code assumes that 10.32403 might be a valid input. If that is not the case you need to decide whether x_values(end) exactly is a valid input and if so whether you want it to go into the bin that starts at x_values(end-1) -- e.g., should 10 exactly go into the same bin as [9,10) or should it go into a bin by itself. If you want it to go into the same bin as [9,10), making that bin [9,10] (inclusive on both sides), an asymmetry as all the other bins will be semi-open, then

[~, binx] = histc(x, [reshape(x_values(1:end-1),[],1); inf]);

Also this assumes that there are no values lower than x_values(1). If there are then do you want them discarded or do you want them placed in a bin by themselves, or do you want them in the same bin as the first defined range?