Filling up zeros forward/backward columnwise

Hi I need to fill up zeros by the previous data columnwise in a matrix containing 5 minutes data for 10 days. each day I have 288 data so total number of rows is 288*10=2880 and number of column if say, 5. if the first data of a given day is zero it will filled up with the next data. Can anybody help by proving MATLAB codes for doing this?

[Walter Roberson]

Is it possible for there to be two 0 in a row? Is it possible for a row to be all 0 ?

[Mohammad Sayeed]

Yes it is possible to have two 0 in a row, but the zeros must be filled up by the previous value in the column if it is not the first value of the day. If is it the first value then it must be filled up with a subsequent data which has a non-zero value.

Answer 1

[Image Analyst]

Something like this maybe (untested)

[rows, columns] = size(m);
for row = 1 : rows
  for col = 2 : columns
    if m(row, col) == 0
      m(row, col) = m(row, col-1);
    end
  end
end

[Mohammad Sayeed]

Thank you for your codes. First your codes are filling up data row-wise while i need to fill up data columnwise. but I can fix up the problem by using transpose command. Second and more importantly, if the first data of each day is zero then it must be filled up with the next available nonzero data. That means if I have 288 data per day and if every 289th data (first data of each data) is zero then it will be filled up by the next available nonzero data. Can you help me to find the codes for that problem please?

[Image Analyst]

You said columnwise so I thought you wanted to go across columns first, in a given row, and then move down to the next row once all the columns in the active row have been processed. I think column-wise means columns first, then rows. I guess you and I have different definitions of column-wise. So you want to go down rows first, and then move over to the next column once all the rows in that column have been processed. Try this (again, untested):

[rows, columns] = size(m);
for col = 1 : columns
  % Fill up zeros if column starts with zero.
  if m(1, col) == 0
    % First row of this column is zero.
    firstNonZeroRow = find(m(:, col)~= 0, 1, 'first');
    % Make all prior rows have that value.
    valueToUse = m(firstNonZeroRow, col); % Get the value.
    m(1:firstNonZeroRow-1, col) = valueToUse;
  end
  for row = 2 : rows
    if m(row, col) == 0
      m(row, col) = m(row, col-1);
    end
  end
end

[Mohammad Sayeed]

Thank you again and sorry for the misunderstanding. I think my problem is more complex than what your codes will solve. May be I should have posted a sample dataset to make it clear. However, I will get some good insights from your codes to solve my problem. Thank you again.

Answer 2

[Jos (10584)]

This looks like a job for FILLZERO :

http://www.mathworks.com/matlabcentral/fileexchange/19906-fillzero-v2-1-may-2008

[Jos (10584)]

and if you want it backward, use FLIPUD before and after.

[Mohammad Sayeed]

Hi Jos, FILLZERO is not working in my MATLAB software. does it require any toolbox?

[Jos (10584)]

Not working is too vague … What is the problem? Note that you need to perform these steps for a File Exchange file to work on your system:

1. Download the file from the File Exchange (and unzip it)
2. Copy the m-file to a specific folder (e.g. "Useful_mfiles") somewhere in your user or programming folder (not in a systems or matlab folder).
3. Add this folder to the matlab path