How can i find rows or coulmns which contain maximum zeroes?

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Uet 2014-5-21

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评论： Star Strider 2014-5-25

Hi, I want to select rows or coulmns which contain maximum zeros? can anyone please help me how to write a script file for this.. I want to develop a simple program for Assignment method..

Reagards,

Ateeq

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Answer 1

Star Strider 2014-5-22

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This will give you the number of zeros in particular rows and columns:

M = [105 0 55 15;  15 0 25 75;  55 0 0 10;  0 0 5 0];
[zr,zc] = find(M == 0);
Z = accumarray([zr zc], 1 )
rowzeros = sum(Z,2)
colzeros = sum(Z,1)

produces:

rowzeros =
       1
       1
       2
       3
colzeros =
       1     4     1     1

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Star Strider 2014-5-23

在 MATLAB Online 中打开

Add after my previous code:

uncr = find(rowzeros < 2);          % Find uncovered rows
uncc = find(colzeros < 2);          % Find uncovered cols
Munc = M(uncr,uncc);                % Uncovered rows & cols (diagnostic)
cvrr = find(rowzeros >= 2);         % Find covered rows
cvrc = find(colzeros >= 2);         % Find covered cols
M(cvrr,:) = M(cvrr,:) + 15;         % Add 15 to covered rows
q = find(M(:,cvrc)<15);             % Test for intersections
M(q,cvrc) = M(q,cvrc) + 15;         % Add 15 to the others
M(uncr,uncc) = M(uncr,uncc) - 15    % Subtract 15 from the uncovered areas

I calculate Munc to be sure I have identified those correctly. The q line was necessary because of the intersections of column 2 and rows 3 and 4. I had to be sure I didn’t add 15 to elements I had already added it to in the previous lines. I couldn’t get logical indexing or arrayfun to work here, because I am only operating on some elements of the matrix and not the entire matrix.

I can’t promise that this will be robust for all such situations, but it works here. Have fun with it!

Uet 2014-5-25

Thank you very much... it works perfect.

Star Strider 2014-5-25

My pleasure!

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Answer 2

Romain 2014-5-21

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If you want the row and the colum with the maximum of values equal to zeros, I propose (for a 2D matrix) :

[numberOfZeroCol,colWithMaxZero] = max(sum(array == 0, 1))
[numberOfZeroRow,rowWithMaxZero] = max(sum(array == 0, 2))

but I'm not sure that's what you want.

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Uet 2014-5-22

Actually I want to find number of rows and coulumns which contain more than two zeroes as covered by color lines in given picture. Then subtract 15 (which is minimum of all uncovered numbers) from all uncovered numbers.

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How can i find rows or coulmns which contain maximum zeroes?

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