group coordinates according to the value of z

Question

Alberto Acri 2022-12-7

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1872902-group-coordinates-according-to-the-value-of-z

评论： Askic V 2022-12-7

采纳的回答： Askic V

coordinate.txt

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Hi. Attached is the file "coordinates.txt".

I would like to group the coordinates of an mx3 array based on the value of z and place each group of values (with equal z) inside different cells.

The image shows what I would like to do.

I am starting like this. How can I modify it?

coordinate = importdata('coordinate.txt');
z_coordinate = coordinate(:,3);
for jj = 1:length(z_coordinate)
    Group{jj} = z_coordinate(jj,:);
end

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Answer 1

Askic V 2022-12-7

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https://ww2.mathworks.cn/matlabcentral/answers/1872902-group-coordinates-according-to-the-value-of-z#answer_1122137

编辑：Askic V 2022-12-7

在 MATLAB Online 中打开

I would start like this:

coordinate = importdata('coordinate.txt');
z_coordinate = unique(coordinate(:,3));
N = numel(z_coordinate);
cell_group = cell([],N);
for ii = 1: N
    ind = find(coordinate(:,3) == z_coordinate(ii));
    cell_group{ii} = coordinate(ind,1:2);
end
cell_group{1}

This will produce 1x6 cell array:

cell_group =
  1×6 cell array
    {9×2 double}    {6×2 double}    {13×2 double}    {11×2 double}    {3×2 double}    {11×2 double}

I'm sure there is even more efficient way to do this, but there are real gurus here who can help.

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Alberto Acri 2022-12-7

I thank you @Askic V! If I wanted to keep within each cell the z coordinates as well?

Askic V 2022-12-7

在 MATLAB Online 中打开

in that case, the line

cell_group{ii} = coordinate(ind,1:2);

becomes

cell_group{ii} = coordinate(ind,:);

First element of cell_group is then:

ans =
0000  329.0000    5.9649
0000  328.0000    5.9649
0000  327.0000    5.9649
0000  326.0000    5.9649
0000  325.0000    5.9649
0000  324.0000    5.9649
0000  323.0000    5.9649
0000  322.0000    5.9649
0000  330.0000    5.9649