CODEWITHSUNDEEP
matlabcell
Not Bo Styf
Not Bo Styf

Reputation: 411

Best way to count all elements in a cell array?

I want to count all elements in a cell array, including those in "nested" cells.

For a cell array

>> C = {{{1,2},{3,4,5}},{{{6},{7},{8}},{9}},10}

C = {1x2 cell}    {1x2 cell}    [10]

The answer should be 10.

One way is to use [C{:}] repeatedly until there are no cells left and then use numel but there must be a better way?

Upvotes: 7

Views: 5428

Answers (2)

Amro
Amro

Reputation: 124553

Since you are only interested in the number of elements, here is a simplified version of flatten.m that @Ansari linked to:

function n = my_numel(A)
    n = 0;
    for i=1:numel(A)
        if iscell(A{i})
            n = n + my_numel(A{i});
        else
            n = n + numel(A{i});
        end
    end
end

The result:

>> C = {{{1,2},{3,4,5}},{{{6},{7},{8}},{9}},10};
>> my_numel(C)
ans =
    10

EDIT:

If you are feeling lazy, we can let CELLPLOT do the counting:

hFig = figure('Visible','off');
num = numel( findobj(cellplot(C),'type','text') );
close(hFig)

Basically we create an invisible figure, plot the cell array, count how many "text" objects were created, then delete the invisible figure.

This is how the plot looks like underneath:

screenshot

Upvotes: 9

Ansari
Ansari

Reputation: 8218

Put this in a function (say flatten.m) (code from MATLAB Central):

function C = flatten(A)
C = {};
for i=1:numel(A)  
    if(~iscell(A{i}))
        C = [C,A{i}];
    else
       Ctemp = flatten(A{i});
       C = [C,Ctemp{:}];
    end
end

Then do numel(flatten(C)) to find the total number of elements.

If you don't like making a separate function, you can employ this clever (but nasty) piece of code for defining a flatten function using anonymous functions (code from here): 

flatten = @(nested) feval(Y(@(flat) @(v) foldr(@(x, y) ifthenelse(iscell(x) | iscell(y), @() [flat(x), flat(y)], @() {x, y}), [], v)), nested);

Either way, you need to recurse to flatten the cell array then count.

Upvotes: 2

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