Intersecting and non-intersecting box regions

Question

Elysi Cochin 2021-7-10

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https://ww2.mathworks.cn/matlabcentral/answers/875768-intersecting-and-non-intersecting-box-regions

评论： Matt J 2021-7-12

bbx.mat

Having a set of bounding box values [x y width height] , how can i find the number of bounding box that gets intersected and that do not gets intersected when plotted

From the above example, there are 5 intersecting boxes and 2 non-intersecting boxes

How can i do so with the attached bounding box values

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Answer 1

Matt J 2021-7-10

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https://ww2.mathworks.cn/matlabcentral/answers/875768-intersecting-and-non-intersecting-box-regions#answer_744048

编辑：Matt J 2021-7-10

在 MATLAB Online 中打开

bbx.mat

Using rectint(), you can straightforwardly obtain a binary mask A such that A(i,j)=1 if rectangle bbx(i,:) and bbx(j,:) intersect.

load bbx
A=rectint(bbx,bbx)>0
A = 20×20 logical array
 1   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0
 1   0   0   0   1   0   0   0   0   0   0   0   0   0   0   0   0   0   0
 0   1   0   0   0   1   0   0   0   0   0   0   0   0   0   0   0   0   0
 0   0   1   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0
 0   0   0   1   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0
 1   0   0   0   1   0   0   0   0   0   0   0   0   0   0   0   0   0   0
 0   1   0   0   0   1   0   0   0   0   0   0   0   0   0   0   0   0   0
 0   0   0   0   0   0   1   0   0   0   0   0   0   0   0   0   0   0   0
 0   0   0   0   0   0   0   1   0   0   0   0   0   0   0   0   0   0   0
 0   0   0   0   0   0   0   0   1   0   0   0   0   0   0   0   0   0   0

and therefore the number of rectangles that have an intersection another rectangle would be,

N=sum(tril(A,-1),'all')

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Elysi Cochin 2021-7-12

编辑：Elysi Cochin 2021-7-12

在 MATLAB Online 中打开

load bbx
A = rectint(bbx,bbx)>0

Sir there are total 20 boxes

and non-intersecting box = 13, but there are more zeros, in the matrix A

So Sir, if I use A(i,j), how will i get 13?

Matt J 2021-7-12

在 MATLAB Online 中打开

>> nnz(sum(A,1)==1)
ans =
    13

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Answer 2

Simon Chan 2021-7-10

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https://ww2.mathworks.cn/matlabcentral/answers/875768-intersecting-and-non-intersecting-box-regions#answer_743928

在 MATLAB Online 中打开

If viusal inspection is allowed, then the number can be counted by plotting the boxes in a figure:

rawdata=load('bbx.mat');
figure
for k=1:length(rawdata.bbx)
    rectangle('Position',rawdata.bbx(k,:))
end

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Elysi Cochin 2021-7-10

在 MATLAB Online 中打开

when i increase the number of rows in bbx, i get error

Matrix dimensions must agree.
Error in demo 
    B = B+A;

Simon Chan 2021-7-10

在 MATLAB Online 中打开

Would you please run the following commands before the above script:

clear;
clc;

If the error happens again, would you please run the following:

size(A)         % Check the dimension of Matrix A
size(B)         % Check the dimension of Matrix B

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Answer 3

KSSV 2021-7-10

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https://ww2.mathworks.cn/matlabcentral/answers/875768-intersecting-and-non-intersecting-box-regions#answer_743923

Run a loop for each box and find the intersection points. Use this to get the intersection points.

https://in.mathworks.com/matlabcentral/fileexchange/22441-curve-intersections.

If your output is empty, it means there is no intersection.

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KSSV 2021-7-10

You have origin, length and width of bounding box. So you can get four vertices of the box. You need to use four coordinates for each bounding box to get the intersection points.

Elysi Cochin 2021-7-10