Convert matrix into the tensor

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Alan
Alan 2012-1-28
Hi, I have some doubts about how can i convert a matrix into the Tensor... My situation: I have a matrix of 250X24, being that first column is associate the plant species while second column represent substances. However, for each substance were performed 22 experiments resulting on values. I want to convert this matrix into the tensor way where I have in the rows, the species, in the columns, substances and to each substance a third dimension corresponding the values of 22 experiments Here is a example of matrix,
1 60 0 1 1 0
2 60 0 1 1 0
3 11 1 1 1 0
3 17 1 1 1 0
3 18 1 1 1 0
3 20 1 1 1 0
3 22 1 1 1 0
3 28 1 1 1 0
3 33 1 1 1 0
3 37 1 1 1 0
3 48 1 1 1 0
3 49 1 1 1 0
3 52 1 1 1 0
3 55 1 1 1 0
4 11 3 1 1 0
4 17 3 1 1 0
first column are species, second, number of the substance, i.e., I want to organize this first row in the this manner: 1 row, sixth column and third dimension the rest (0 ,1 ,1, 0 son on)... Sorry If I don't get explain correctly Thanks
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Andrew Newell
Andrew Newell 2012-1-29
The number of elements (250x24) is not divisible by 22, so apparently not all 22 experiments were performed on each substance.

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Andrew Newell
Andrew Newell 2012-1-29
This is not a tensor, which has a specific meaning. If you had the same number of experiments per substance, you could turn it into a 3D array. For a variable number of experiments you will need a cell array. Here is one approach:
First, determine the distinct species and substances. species = unique(M(:,1)); substances = unique(M(:,2));
Create a cell array of the appropriate size.
nspec = numel(species);
nsub = numel(substances);
Marray = cell(nspec,nsub);
Populate each combination of species and substance with a matrix of experimental results.
for ii=1:nspec
for jj=1:nsub
[r,c] = find(M(:,1)==species(ii) & M(:,2) == substances(jj));
Marray{ii,jj} = M(r,3:end);
end
end
Here is how you retrieve the results for species 3 and substance 22:
ii = find(species==3); jj = find(substances==22);
Marray{ii,jj}
ans =
1 1 1 0

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