Convert matrix into the tensor

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

[Andrew Newell]

The number of elements (250x24) is not divisible by 22, so apparently not all 22 experiments were performed on each substance.

Answer 1

[Andrew Newell]

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

[Alan]

Thanks,

It's working perfectly.