Ordering a matrix as x increases and y increases

Question

Alberto Acri 2023-10-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2038481-ordering-a-matrix-as-x-increases-and-y-increases

编辑： Voss 2023-10-26

采纳的回答： Voss

square.mat

在 MATLAB Online 中打开

Hi. I need to remove repeating nodes inside the 'square' array (I need to get only unique rows without repetition).

I tried with the 'unique' command which should be the correct solution, but I would like to confirm.

load square.mat
square = unique(square, 'rows');
figure
plot(square(:,1),square(:,2),'g.','Markersize',15);
axis equal
set(gca, 'YDir','reverse')

Then I need to sort the matrix so that I have the coordinates in the following order:

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Answer 1

Voss 2023-10-25

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2038481-ordering-a-matrix-as-x-increases-and-y-increases#answer_1340591

在 MATLAB Online 中打开

square.mat

square = unique(square,'rows'); works to remove repeated rows, yes.

In I uderstand the ordering you want, it is to sort by y-coordinate (increasing) and where y-coordinates are equal sort by x-coordinate (increasing). You can sort square in this manner using square = sortrows(square,[2 1]);

load square
square = unique(square,'rows');
square(1:5,:)
ans = 5×2
  -89.7000 -108.0000
  -89.7000 -107.5781
  -89.7000 -107.1563
  -89.7000 -106.7344
  -89.7000 -106.3125
square = sortrows(square,[2 1]); % sort by y, then by x
square(1:5,:)
ans = 5×2
  -89.7000 -108.0000
  -89.2781 -108.0000
  -88.8562 -108.0000
  -88.4344 -108.0000
  -88.0125 -108.0000

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Alberto Acri 2023-10-26

Thank you @Voss! What if I wanted to modify the 'square' matrix like this way instead?

Voss 2023-10-26

编辑：Voss 2023-10-26

在 MATLAB Online 中打开

square.mat

load square
square = unique(square,'rows');
square(1:5,:)
ans = 5×2
  -89.7000 -108.0000
  -89.7000 -107.5781
  -89.7000 -107.1563
  -89.7000 -106.7344
  -89.7000 -106.3125
square = sortrows(square,[-2 1]); % sort by y (decreasing), then by x (increasing)
square(1:5,:)
ans = 5×2
  -89.7000  107.5781
  -89.2781  107.5781
  -88.8562  107.5781
  -88.4344  107.5781
  -88.0125  107.5781