How does one concatenate cell arrays that are part of a cell array in MATLAB?
Solution 1
There are a few more details about your cell contents that would be needed for a more general solution, but if the names
property always returns a cell array of strings, and if your structures are all scalars (i.e. 1-by-1 structure arrays), then the following solution using CELLFUN, CHAR, and CELLSTR will give you an N-by-1 cell array of strings allNames
containing all of your names:
allNames = cellfun(@(x) {char(x.names)},allData);
allNames = cellstr(char(allNames{:}));
And here's an example where allData
contains three different structures:
>> allData{1} = struct('names',{{'hello'}},'junk',1:3);
>> allData{2} = struct('names',{{'hi' 'yo' 'hey' 'whassup'}});
>> allData{3} = struct('names',{{'howdy';'aloha'}},'junk',4);
>> allNames = cellfun(@(x) {char(x.names)},allData);
>> allNames = cellstr(char(allNames{:}))
allNames =
'hello'
'hi'
'yo'
'hey'
'whassup'
'howdy'
'aloha'
EDIT:
Generalizing to the case where the names
property returns a cell array of objects, not necessarily strings, you can try this solution which reshapes each cell array into an M-by-1 cell array, then vertically concatenates all of them into an N-by-1 cell array of objects:
allNames = cellfun(@(x) {reshape(x.names,[],1)},allData);
allNames = vertcat(allNames{:});
Or, if you would rather end up with a 1-by-N cell array of objects, you can do this:
allNames = cellfun(@(x) {reshape(x.names,1,[])},allData);
allNames = [allNames{:}];
Solution 2
Try this
allNames = arrayfun(@(x) x.name, [allData{:}], 'UniformOutput', false)
Omit the UniformOutput vararg for straight concatenation. This gives a cell output.
Comments
-
PengOne almost 2 years
I have a cell array
allData
which is Nx1. Each cell contains a structure with anames
property (the name is a custom object, but think of it as a cell array of strings if you like). I would like to create a single cell array that contains all of the names. For example, if N=3, so thatallData
is a 3x1 cell array, then the following would accomplish my goal:A = allData{1}; B = allData{2}; C = allData{3}; allNames = [A.names B.names C.names];
The problem with this approach is that N is large and changes depending on the input, so I'm hoping that there is a clever way to do this using
cellfun
, but everything that I've tried fails (e.g. it doesn't work to doallNames = [cellfun(@(x) {x.names}, allData)];
).UPDATE: Thanks to the suggested solutions, I can get everything into one cell array where each cell contains a cell array. My goal here is to concatenate these. More or less, what I have is:
{A.names B.names C.names}
and what I want and cannot seem to get is
{A.names{1} A.names{2} ... A.names{end} B.names{1} ... B.names{end} ...}
SOLUTION: I needed pieces of each answer below, so here's the solution that worked for me:
from Andrew Lazarus:
allNames = arrayfun(@(x) x.name, [allData{:}], 'UniformOutput', false);
then, from gnovice:
allNames = vertcat(allNames{:});
Thanks to both!!
-
gnovice almost 13 yearsThe operation
[allData{:}]
will only work if the elements of the cell array can be horizontally concatenated into a structure array, which would mean there was no real reason to use a cell array in the first place. -
PengOne almost 13 yearsThis is great if they are cell arrays of strings, but sadly I misled you. They are cell arrays of custom objects. Still, I may be able to get some mileage out of this approach. Thanks!
-
Richie Cotton almost 13 years@PengOne: The moral of the story being "remember to provide sample data in your question".
-
Andrew Lazarus almost 13 years@PengOne: note the [brackets]. But I'll try for a more generic solution.
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PengOne almost 13 years@Richie Cotton: The object is defined over several files and many, many lines, so it only clouds the question which at the heart is simple: How can I concatenate cell arrays that themselves are cells in a cell array?
-
PengOne almost 13 yearsTried this... result is a 1x3 cell array, each cell containing one of the cell arrays that I truly wish would just find a way to concatenate themselves!
-
gnovice almost 13 years@PengOne: I've updated my answer to deal more generally with objects as opposed to strings.
-
PengOne almost 13 yearsJessumCrow! The
vertcat
function worked (once I transposed correctly)! Thanks for this. I did not need to reshape for my example, but please leave it in your solution in case someone else beats his head against the wall on this one. -
Andrew Lazarus almost 13 years@PengOne, Not quite sure what you mean, but a possibility: By changing UniformOutput to true, you get array output. That is the default anyway. You may need to transpose the output to get a concatenated single string.