repeat rows in a matrix based on values in one column

Hello All,

I have a matrix which is attached here. Here is what I want to do: I want to make a duplicate of rows whose first column values are the same and then put the duplicate right beneath when the value of the first column changes. I have put a picture for portion of the final file that I want. Thanks for your help.

Answer 1

[dpb]

u=unique(x(:,1),'stable');       % get the unique values in first column to work over; keep original order
xx=[];
for i=numel(u):1
  ix=find(x(:,1)==u);
  xx=[xx;repmat(x(ix,:),2,1)];   % build the new output array
end

"Deadahead" to just copy the sections to a new file; if not _terribly large x the dynamic reallocation shouldn't be too bad.