Can I sort Find function base on rows?

Question

bkshn 2014-3-3

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回答： Julian 2023-8-3

Hello

I use find function to find location of a vector on my Image, It works, but I have location Order by column.I mean at firs I have location of pixels on column1 then column2,..... Can I change find function to have location of pixels on row1,row2,.....?

I'll appreciate your help.

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Image Analyst 2014-3-4

编辑：Image Analyst 2014-3-4

I agree - totally confusing. Posting the image would probably help, as well as reading this. And say what you want to do once you have this. Because I suspect you don't even need it. I think you might be able to do what you want to do just with a binary image - no need to get (x,y) coordinates of every single non-zero pixel. I mean, why? Why do you think you need that? There are some situations (e.g. edge linking) but I'd like to know your reason.

bkshn 2014-3-5

编辑：Walter Roberson 2014-3-15

Hello Image Analyst

I'm working on seam carving(one of content aware image resizing methods).Then I need to khnow location of seam to cut it from my Image.I try to attach my image or insert it, But I can't do it compeletly. as you see I have a vector on the left of my image.

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Answer 1

Julian 2023-8-3

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https://ww2.mathworks.cn/matlabcentral/answers/120016-can-i-sort-find-function-base-on-rows#answer_1282787

I couldn't find a nice solution in the documentation, so I assume the best way is instead of:

A = [1 0;

0 1;

1 0];

[row, col] = find(A);

% Results:

% row = [1; 3; 2]

% col = [1; 1; 2]

Transpose the matrix A and exchange the row and column:

[col, row] = find(A.');

% Results:

% row = [1; 2; 3]

% col = [1; 2; 1]

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Answer 2

Walter Roberson 2014-3-4

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https://ww2.mathworks.cn/matlabcentral/answers/120016-can-i-sort-find-function-base-on-rows#answer_126949

在 MATLAB Online 中打开

[row, col] = find(.....);
cr = sortrows([col(:), row(:)];
r = cr(:,2);
c = cr(:,1);

now r(K), c(K) is a (row, column) pair and the pairs are ordered so that column varies more slowly. But it normally would anyhow. So perhaps what you want is

[row, col = find(.....);
rc = sortrows([row(:), col(:)]);
r = rc(:,1);
c = rc(:,2);

and that should be ordered with row varying more slowly, "going along rows", the opposite of what would normally happen.

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bkshn 2014-3-16

I have a 5*2 matrix like A=[3,4;2,5;1,6;4,7;5,9;]

your answer sort this like A=[1,4;2,5;3,6;4,7;5,9;] , as you see it sort rows and column

but I want to sort just rows like

A=[1,6;2,5;3,4;4,7;5,9;]

Walter Roberson 2014-3-16

sort(A,2)

but you are now not working with vectors returned from find(), which are indices with row(K) corresponding to col(K) after the find and row(K), col(K) giving the location of what was found; you are now sorting by array content based upon the full array, which is a different task.

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