half the first NaN value after the last non NaN value in each column

Hi, I have a matrix

p = [NaN   2   NaN;
       2   4   NaN;
       2   6   8;
       NaN 8   2;
       NaN NaN 1;
       NaN NaN 1]

The realized matrix

p1 = [NaN 2 NaN;
      2 4 NaN;
      2 6 8;
      1(half of 2) 8 2;
      NaN 4(half of 8) 1;
      NaN NaN 1]

... Notice: Only the first NaN after the last non NaN value in each column is halved with the last non NaN value.. while the other NaN stay as they were.. Thank you for your answers. BR

Answer 1

[Jan]

p = [NaN 2   NaN;
       2 4   NaN;
       2 6   8;
     NaN 8   2;
     NaN NaN 1;
     NaN NaN 1];
m = isnan(p);
for col = 1:size(p, 2)
  index = strfind(m(:, k).', [false, true]);   % [EDITED]
  if ~isempty(index)
    p(index(1) + 1, k) = p(index(1), k) / 2;
  end
end

[Qian cao]

sorry ... it does not work out

[Jan]

Please, Qian cao, giv us any chance to post an improvement. Tell us, what goes wrong. Do you get an error message or does the result differ from your expectations? I see a little typo, which is fixed now. So try it again.

Answer 2

[Thorsten]

ind = diff(isnan([p; p(end,:)])) == 1;
p(ind) = p(ind)/2;

[Qian cao]

No...it should be the cell after p(ind)...I tried with p(ind+1) = p(ind)/2; But it does not work...Could you help me ? In your result, the last non NaN is replaced...but I need to keep it and just fill the cell after it in the column with a value that is half of it...

[Thorsten]

Use

ind = find(diff(isnan([p; p(end,:)])) == 1);
p(ind+1) = p(ind)/2;