How to get ( number and values) of (non-empty elements) in each column of the matrix??

Hi all, I have the following matrix;

P = 
  Columns 1 through 2
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x2 double]    [2x2 double]
    [2x2 double]    [2x2 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
  Columns 3 through 4
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x2 double]
    [2x2 double]    [2x2 double]
    [2x2 double]    [2x2 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]

I want to get the number of the non-empty elements in each column and then their values.

For example; in Column 1, there are two non-empty elements [2x2 double]. To get their values; I should write like that; P{row_no,1} ;

 >> P{7,1}
  ans =
         0.5878      0.71222
              0            0
  >> P{8,1}
  ans =
        0.78307        1.117
              0            0

So, My question is; how to get the number of the non-empty elements in each column and also how to get the values of these non-empty elements?

[Image Analyst]

Original question from Erman (in case he decides to delete this one also):

How to get (the number and the values) of the (non-empty elements "[2x2 double] elements") in each column of the matrix??

Hi all, I have the following matrix;

P = 
  Columns 1 through 2
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x2 double]    [2x2 double]
    [2x2 double]    [2x2 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
  Columns 3 through 4
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x2 double]
    [2x2 double]    [2x2 double]
    [2x2 double]    [2x2 double]
    [2x0 double]    [2x0 double]
    [2x0 double]    [2x0 double]

I want to get the number of the non-empty elements in each column and then their values.

For example; in Column 1, there are two non-empty elements [2x2 double]. To get their values; I should write like that; P{row_no,1} ;

 >> P{7,1}
  ans =
         0.5878      0.71222
              0            0
  >> P{8,1}
  ans =
        0.78307        1.117
              0            0

So, My question is; how to get the number of the non-empty elements in each column and also how to get the values of these non-empty elements?

Answer 1

[Walter Roberson]

nonempty_col1_mask = ~cellfun(@isempty, P(:,1));
nonempty_col2_mask = ~cellfun(@isempty, P(:,2));
num_nonempty_col1 = nnz(nonempty_col1_mask);
num_nonempty_col2 = nnz(nonempty_col2_mask);
nonempty_col1 = P(nonempty_col1_mask, 1);
nonempty_col2 = P(nonempty_col2_mask, 2);

[Eman S]

@ Walter Roberson

Thanks so much for your help. It worked. But, if I want to use the (for loop) get the non-empty elements of the matrix and their values, for each column.

I tried to do that as following code;

for j=1:4
     nonempty_col{j} = ~cellfun(@isempty, P(:,j));
     num_nonempty_col(j) = nnz(nonempty_col{j});
     nonempty_values_col{j} = P(nonempty_col{j}, j);
end

It works fine. But, the last line which used to get the values of the non-empty elements, did not give their values. It gave the following, after running the code;

nonempty_values_col = 
  Columns 1 through 3
    {2x1 cell}    {2x1 cell}    {2x1 cell}
  Columns 4 
    {3x1 cell}

To get the values of specific column, it gave their values as following;

nonempty_values_col{1}
ans = 
    [2x2 double]
    [2x2 double]

So, what is the error in this code?? How can I modify it to work fine with for loop to get the values of the non-empty elements in each column??

[Walter Roberson]

I do not see any problem? Each column has entries which are 2D arrays, and the code correctly pulls out the 2D arrays into individual locations.

If you want all of the the 2D arrays merged together, giving a single 4 x 2 array for each of columns 1, 2, and 3, and a 6 x 2 array for column 4, then cell2mat(P(nonempty_col{j}, j)) .

[Eman S]

Ok. Thanks.