How to reshape matrix by column number?

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Emma Kuttler
Emma Kuttler 2022-4-19
编辑： Stephen23 2022-4-19
Hi, I have a 163 x 13 matrix of numerical values that I'd like to turn into a longer matrix. I'd like to keep the first two columns the same, but output the column number in a new column (starting with column 3 assigned the key 1), and then the value for that column in the next column. Then I'd like to remove rows with zero in the fourth column.
For example, if "demand" is my matrix, I want to produce "demandlong"
demand = [1 78 0 0 0 0 0 0 0 0 8 45 0
1 79 0 0 0 0 31 8 0 0 0 0 0
1 80 456 0 4 0 39 0 0 0 16 0 0]
demandlong =
[1 78 10 45
1 79 5 31
1 80 1 456
1 80 3 4
1 80 5 39
1 80 9 16]

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回答（2 个）

Stephen23
Stephen23 2022-4-19
Ran in:
D = [1,78,0,0,0,0,0,0,0,0,8,45,0;1,79,0,0,0,0,31,8,0,0,0,0,0;1,80,456,0,4,0,39,0,0,0,16,0,0]
D = 3×13
1 78 0 0 0 0 0 0 0 0 8 45 0 1 79 0 0 0 0 31 8 0 0 0 0 0 1 80 456 0 4 0 39 0 0 0 16 0 0
M = D(:,3:end).';
[C,R] = find(M);
Z = [D(R,1:2),C,nonzeros(M)]
Z = 8×4
1 78 9 8 1 78 10 45 1 79 5 31 1 79 6 8 1 80 1 456 1 80 3 4 1 80 5 39 1 80 9 16
  2 个评论
Emma Kuttler
Emma Kuttler 2022-4-19
Thanks! How would you modify the code if you wanted to also return the rows with zero in them?
Stephen23
Stephen23 2022-4-19
编辑：Stephen23 2022-4-19
Ran in:
"How would you modify the code if you wanted to also return the rows with zero in them?"
Do you mean something like this?:
D = [1,78,0,0,0,0,0,0,0,0,8,45,0;1,79,0,0,0,0,31,8,0,0,0,0,0;1,80,456,0,4,0,39,0,0,0,16,0,0]
D = 3×13
1 78 0 0 0 0 0 0 0 0 8 45 0 1 79 0 0 0 0 31 8 0 0 0 0 0 1 80 456 0 4 0 39 0 0 0 16 0 0
M = D(:,3:end).';
S = size(M);
[C,R] = ndgrid(1:S(1),1:S(2));
Z = [D(R,1:2),C(:),M(:)]
Z = 33×4
1 78 1 0 1 78 2 0 1 78 3 0 1 78 4 0 1 78 5 0 1 78 6 0 1 78 7 0 1 78 8 0 1 78 9 8 1 78 10 45

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KSSV
KSSV 2022-4-19
Ran in:
demand = [1 78 0 0 0 0 0 0 0 0 8 45 0
1 79 0 0 0 0 31 8 0 0 0 0 0
1 80 456 0 4 0 39 0 0 0 16 0 0] ;
n = size(demand,1) ;
iwant = zeros(n,4) ;
iwant(:,1:2) = demand(:,1:2) ;
for i = 1:n
id = find(demand(i,:)) ;
iwant(i,3) = id(3)-2 ;
iwant(i,4) = demand(i,id(3)) ;
end
iwant
iwant = 3×4
1 78 9 8 1 79 5 31 1 80 1 456

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