Select a row and append it at the end of a matrix | Move a selected row to end of matrix

Question

Rishi Balasubramanian 2020-12-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/697310-select-a-row-and-append-it-at-the-end-of-a-matrix-move-a-selected-row-to-end-of-matrix

评论： Rishi Balasubramanian 2020-12-18

采纳的回答： Matt J

Hello People,

Assume i have a matrix H =

[1 0 0 1

0 1 0 0

1 1 1 0

1 1 0 1

0 1 0 1

0 0 1 1]

Now I want to move row number 2 and 4 to the end of the matrix. NOT SWAP.

Like removing row 2 & row 4 and appending them after row 6. The remaining rows cascade upward in the same order.

I need pointers on how to achieve this. I unknowingly used swap and realised that it was the reason my algorithm failed. Any help would be appreciated.

Thank You

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KALYAN ACHARJYA 2020-12-18

在 MATLAB Online 中打开

data=H([1,3,5,6,2,4],:)

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Answer 1

Matt J 2020-12-18

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/697310-select-a-row-and-append-it-at-the-end-of-a-matrix-move-a-selected-row-to-end-of-matrix#answer_579180

编辑：Matt J 2020-12-18

在 MATLAB Online 中打开

 
H=[1    0    0    1
 0    1    0    0
 1    1    1    0
 1    1    0    1
 0    1    0    1
 0    0    1    1];
rows2move=[2,4];
idx=[setdiff(1:size(H,1), rows2move), rows2move];
H=H(idx,:)
H = 6×4
     1     0     0     1
     1     1     1     0
     0     1     0     1
     0     0     1     1
     0     1     0     0
     1     1     0     1
●

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Rishi Balasubramanian 2020-12-18

编辑：Rishi Balasubramanian 2020-12-18

在 MATLAB Online 中打开

PCMatrix.mat

So I am trying to adapt this to my code, but it says dimensions are not consistent. I am attaching the actual matrix (93x155) and the code which I am trying to generalise. Could you help me on it?

[m, n] = size(H);
for i = 1:n
    a = sum(H);
end
amax = max(a);
amin = min(a);
if (amax == amin)   %select random col if there is no column with min ones
    c1 = n;
else (amax > amin)  %select the col with the min ones
    [r,c] = find(a==min(a));
    c1 = c;
end
%identify rows containing 1's in selected column.
 rows = find(H(:,c1)==1)
 
 %I HAVE FOUND THE ROWS WITH ONES IN IT, I WANT TO MOVE THOSE ROWS TO BOTTOM, HOW DO I DO IT?
 
 %%%%%%%%% UPDATE %%%%%%%%%%
 %SO I tried incorporating it into the code using loops. I feel like I almost got it, but it says index exceeds dimensions
 for i = 1:size(rows)
idx=[setdiff(1:size(H,1), rows(i)), rows(i)];
H = H(idx(i), :);
 end
 
 %COuld you say if this is right?

So the 'rows' will consist of the indexes of the rows that i want to move to after the end of the matrix, i.e. those rows must come after row 155, and the rest of the rows mustn't change except moving up to fill the void. Thanks in advance for your help.

Rishi Balasubramanian 2020-12-18

Yup, got the answer. Thanks a ton man.

Rishi Balasubramanian 2020-12-18

But what I don't understand is this. In my version, i used FIND function to find the indexes of the rows that have 1s in them.

This is your version

rows = H(:,c1)==1;

I don't understand how it works. It works. But i can't figure out how and why. Could you explain it, as I will be using many versions of this across my algorithm. It'll be really helpful.

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