Interleaving columns of two cell arrays

Hey all,

I have two cell arrays:

• ca = 7x9 cell array where each cell is a block of pixels 64x64x3
• ca2 = 7x8 cell array where each cell is a block of pixels 64x64x3

I would like to interleave the cell array by columns like so:

• ca3 = {ca{:,1};ca2{:,1};ca{:,2};ca2{:,2};ca{:,3};ca2{:,3};ca{:,4};ca2{:,4};ca{:,5};ca2{:,5};ca{:,6};ca2{:,6};ca{:,7};ca2{:,7};ca{:,8};ca2{:,8};ca{:,9}}';

I'm sure there has to be a more programmatic way of doing this and in a more extensible fashion(where if I have more then 8/9 columns I wouldn't have to keep adding to the code).

Thanks! Hope this makes sense

Answer 1

[Kirby Fears]

Here's a function I wrote for you. It contains a subfunction to create the interleaving index. Save this to interleaveCells.m and try calling it.

function c = interleaveCells(c1,c2)
% Make index for interleaving cells
ind = interleaveIndex(size(c1,2),size(c2,2));
% Combine cells
c = [c1, c2];
% Interleave cells
c = c(:,ind);

function ind = interleaveIndex(n1,n2)
ind = NaN(1, n1 + n2);
i = 1;
j = 1;
while i<=n1,
    ind(i+j-1) = i;
    i = i + 1;
    if j<=n2,
        ind(i+j-1) = n1 + j;
        j = j + 1;
    end
end
while j<=n2,
    ind(i+j-1) = n1 + j;
    j = j + 1;
end

Hope this helps.

[Raphael Chazelle]

Works like a charm. Thanks!

[Kirby Fears]

Great. I am editing in a change that simplifies the subfunction as well.

Cheers.

Answer 2

[the cyclist]

I think this does what you want

% Your actual data here. (These are empty, but wouldn't be for your application)
ca  = cell(7,9);
ca2 = cell(7,8);

% Append extra, empty column of cells, so that we can concatenate below 
ca2_tmp = [ca2, cell(7,1)];

% Concatenate top-to-bottom, then reshape
ca3 = reshape([ca;ca2_tmp],7,18);

% Trim spurious final column
ca3(:,end) = [];

[Raphael Chazelle]

This one works! the one below is close but not the desired output!

Answer 3

[the cyclist]

ca3 = [ca,ca2];
idx = reshape(1:18,[],2)'
ca3 = ca3(:,idx(1:end-1));

EDIT: Fixed this to get the indexing right. Arguably a bit easier than my other solution, but basically works on the same principle.