How to count the total number of occurrences of each digit in cell arrays?

Suppose I have a cell array

C = {[1; 4; 7]; [2; 5; 8; 9]; [3; 4]};
c{:}
ans = 
1
4
7
ans =
2
5
8
9
ans=
3
4

   % where any digit won't repeat in the individual cell.
   % There are 4 stages in this cell array. 
   % first stage elements are 1, 2, 3
   % second stage elements are 4, 5, 4
   % third stage elements are 7,8
   % fourth stage elements are 9

I need to count the total number of occurrences of each digit in stage 2. Expected output:

Digit | Number of occurrences
  4        2
  5        1

[Guillaume]

Your concept of stage is badly thought. You would be much better off storing stages as element of the cell array rather than scattering them across the elements. So:

 c = {[1 2 3], [4 5 4], [7 8], 9]}

As it is you will have to programmatically convert your existing cell array into the above to do your histogram any way.

Answer 1

[Stephen23]

>> C = {[1; 4; 7]; [2; 5; 8; 9]; [3; 4]};
>> V = cellfun(@(v)v(2),C);
>> U = unique(V);
>> N = histc(V,U);
>> [U,N]
ans =
   4   2
   5   1

[Md Shahidullah Kawsar]

Thanks. What if I also want to include stage 3 and stage 4?

[Stephen23]

"What if I also want to include stage 3 and stage 4?"

Method one: read Guillaume's comment and follow that advice. Then you can use a simple loop:

% Your data:
C = {[1;4;7]; [2;5;8;9]; [3;4]}
% Convert cell array:
X = cellfun(@(v)1:numel(v),C,'uni',0);
X = accumarray([X{:}].',vertcat(C{:}),[],@(v){v})
for k = 1:numel(X)
    U = unique(X{k});
    N = histc(X{k},U);
    [U,N]
end

Giving:

ans =
   1   1
   2   1
   3   1
ans =
   4   2
   5   1
ans =
   7   1
   8   1
ans =
   9   1

Method two: alternatively you could use nested loops and a cellfun call to check the length of the cell contents. The use a loop:

C = {[1;4;7]; [2;5;8;9]; [3;4]}
L = cellfun('length',C)
for k = 1:max(L)
    V = cellfun(@(v)v(k),C(L>=k));
    U = unique(V);
    N = histc(V,U);
    [U,N]
end

Giving:

ans =
   1   1
   2   1
   3   1
ans =
   4   2
   5   1
ans =
   7   1
   8   1
ans =
   9   1

[pedro antonio solares hernandez]

Hello!; it's posible to compute with this example the elements from rows? In this example, the results coming from the columns.

For example, if i have the array C = {[1,1,7,2]; [2,5,8,6]; [3,4,2,2,4,3]}, ill like to have the next result:

row 1:

1-> 2

2-> 1

7->1

row 2:

2-> 1

5-> 1

6-> 1

8-> 1

row 3:

2-> 2

3-> 2

4-> 2