deleting some of the arrays in a matrix based on a principle

Question

Pooneh Shah Malekpoor 2022-2-28

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https://ww2.mathworks.cn/matlabcentral/answers/1660170-deleting-some-of-the-arrays-in-a-matrix-based-on-a-principle

编辑： Matt J 2022-2-28

Hello

I have a matrix of numbers for example: [10; 20; 30; 40; 50; 60; 70; 80; 90;...;160] which are assigned to a mesh in order, the same as the figure below(element size=10). I want to delete the numbers: 40, 80, 120, 160 based on a line which intersects this mesh and only retain [10;20;30;50;60;70;90;100;110;130;140;150] to be my output. How can I code this? Any suggestion is highly appreciated.

Best Regards

Pooneh

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Pooneh Shah Malekpoor 2022-2-28

This is an example line drawn from the top corner of the highest elements to the bottom corner of the first row elements. This line shows the slope of the geometry which I am going to assign values to its elements.

Pooneh Shah Malekpoor 2022-2-28

the final meshing of the geometry should be like this figure:

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Answer 1

Matt J 2022-2-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1660170-deleting-some-of-the-arrays-in-a-matrix-based-on-a-principle#answer_906240

编辑：Matt J 2022-2-28

在 MATLAB Online 中打开

A=reshape(10:10:160,4,4)
A = 4×4
    10    50    90   130
    20    60   100   140
    30    70   110   150
    40    80   120   160
[M,N]=size(A);
[X,Y]=ndgrid(0:M-1,0:N-1);
test=@(x,y) y+4*x-12<=-1e-6; %test if x,y is below the line with 1e-6 tolerance.
keep=test(X,Y)|test(X+0.5,Y)|...  %keep a cell if any of its 4 corners is below the line
     test(X,Y+0.5) | test(X+0.5,Y+0.5); 
result=A(keep)' %[10;20;30;50;60;70;90;100;110;130;140;150] 
result = 1×12
    10    20    30    50    60    70    90   100   110   130   140   150