Split arrays in table into separate rows

Hello everyone,

I have a table - see screenshot for clarification - where some columns consist of one array each, e.g. the columns R2s and MT. One column contains an array with coordinates x, y and z for each of the items in the following arrays, so 6 sets of coordinates in this case in the first row. The other columns contain strings or single numbers, e.g. 'number_of_voxels'.

What I would like to do is to split the arrays and put each item with its corresponding items from all other columns - including the coordinate column - into one row, e.g.

voxel_coord_x voxel_coord_y voxel_coord_z R2s MT number_of_voxels

11 18 30 0.0124 1.6732 6

12 18 32 0.0162 1.4217 6

This would mean that the array with coordinates doesn't only need to be split into separate rows, but also into three columns. Also, I would need the columns with single strings to get repeated for rows that were in the same array, e.g. 'number_of_voxels' in this example.

I know strsplit could be used to separate the items at the semicolon, but I cannot figure out how to move everything into separate rows/columns. Note that not all arrays have the same number of items.

Thank you in advance for any help or tips!

Answer 1

[Duncan Po]

I think you can do what you want in several steps.

% Convert your cell arrays in voxel_coord, R2s, and MT into arrays using cell2mat
t1 = varfun(@cell2mat, t, 'InputVariables', {'voxel_coord', 'R2s', 'MT'});
t1.Properties.VariableNames = {'voxel_coord', 'R2s', 'MT'});  % varfun modifies the names, change them back

% Split voxel_coord into multiple columns
t1 = splitvars(t1, 'voxel_coord', 'NewVariableNames', {'voxel_coord_x', 'voxel_coord_y', 'voxel_coord_z'});

% Finally expand number_of_voxels and scale
t1.number_of_voxels = repelem(t.number_of_voxels, 6);
t1.scale = repelem(t.scale, 6);

[RP]

Thank you so much, this was a great help and (almost) completes the task perfectly!

The only problem is with the last step, expanding the cells that have to stay the same into several rows (here 'number_of_voxels' and 'scale'). These cells don't need to be copied the same number of times, it is not always 6, so the solution with repelem does not work. I tried

for a = 1:length(t.number_of_voxels)
    t1.number_of_voxels(a) = repelem(t.number_of_voxels, a);
end

but of course this is no good because t1 and t don't have the same length so the referencing is not correct. If anyone has an idea that would be wonderful, thank you in advance!

[Duncan Po]

It looks like the number of times you want to copy is equal to number_of_voxels value. Does this work?

% Finally expand number_of_voxels and scale
t1.number_of_voxels = repelem(t.number_of_voxels, t.number_of_voxels);
t1.scale = repelem(t.scale, t.number_of_voxels);

[RP]

That's exactly what I wanted, thank you so so much for your help!