MATLAB: Combining cell arrays with empty doubles

cell arrays

Suppose I have two cell arrays, with 
a = cell(1,2);
a{1} = 1;
b = cell(1,2);
b{2} = 2;
How can I quickly combine the two to give me
1×2 cell array
    {[1]}    {[2]}
?
In general, I want to combine several cell arrays of the same dimension, which at a given index either either all have {0×0 double} doubles or at most one of the cell arrays does not have a {0×0 double} double.
Thanks!
Michael

Best Answer

% slightly more complex example data:
a = {[],1;[],[]};
b = {[],[];2,[]};
c = {[],[];[],NaN};
%
tmp = cat(3,a,b,c);
[~,idp] = sort(cellfun('isempty',tmp),3);
sz = size(tmp);
[idr,idc] = ndgrid(1:sz(1),1:sz(2));
idx = sub2ind(sz,idr,idc,idp(:,:,1));
out = tmp(idx)
out = 2x2 cell array
    {0×0 double}    {[  1]}
    {[       2]}    {[NaN]}
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