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Cell array array of arrays of various sizes into a cell array of cell arrays of size {1xN}

I am trying to unwind a combnk to generate all combinations of rows in a cell. For example:.

someStrings = {'a','b','dog','goat'};
results = arrayfun(@(k) combnk(someStrings,k),1:length(someStrings),'UniformOutput',0);

This gives me a cell array of cell 4*1

arrays with the following dimensions:

{4x1 cell}    {6x2 cell}    {4x3 cell}    {1x4 cell}

What I want is a cell array of cell 15*1

arrays, each with a size {1xN}

; that is, 4 array cells in size {1,1}

, 6 in size {1,2}

, etc. How can I do this efficiently?

EDIT: Ok, now I'm here:

results = transpose(arrayfun(@(k) num2cell(combnk(someStrings,k),2),1:length(someStrings),'UniformOutput',0));
finalResults = vertcat(results{:});

Is it possible to turn this into one line? How do you index a cell array like "{:}", but a cell array was created in the string?

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2 answers


You can achieve this in the following way:

intermResults=cellfun(@(x) num2cell(x,2),results,'uni',0);
finalResults=vertcat(intermResults{:});


Explanation: If you look at your variable results

, you have these 15 cells. You just need to extract each row and make it a cell. This is what it does num2cell(x,2)

. By packing it in cellfun

, I am applying it to every cell in the cell array results

. You now have a cell 1x4

where each row of results has been converted to a separate cell. You just need to concatenate it to get the final answer. What it does vertcat(intermResults{:})

.

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You can do it like this:

m = dec2bin(1:2^numel(someStrings)-1)-'0'; %// each row contains indices of a combination
[~, s] = sort(sum(m,2)); %// compute sum of each row, sort and get sorting indices
m = m(s,:); %// sort rows according to sum
[jj, ii] = find(m.'); %'// find column indices (jj), ordered by row (ii)
result = accumarray(ii, jj, [], @(x){someStrings(x)}); %// group col indices of each row

This gives for your example someStrings

,



>> result
result = 
    {1x1 cell}
    {1x1 cell}
    {1x1 cell}
    {1x1 cell}
    {1x2 cell}
    {1x2 cell}
    {1x2 cell}
    {1x2 cell}
    {1x2 cell}
    {1x2 cell}
    {1x3 cell}
    {1x3 cell}
    {1x3 cell}
    {1x3 cell}
    {1x4 cell}

Where

>> result{1}
ans = 
    'goat'
>> result{2}
ans = 
    'dog'
>> result{3}
ans = 
    'b'
>> result{4}
ans = 
    'a'
>> result{5}
ans = 
    'dog'    'goat'
>> result{6}
ans = 
    'b'    'goat'
[...]
>> result{15}
ans = 
    'a'    'b'    'dog'    'goat'
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