//DATESTR (SDR) 
//  STR = DATESTR(T, N) gives a string column vector of date/time T
//  in format:
//  YYYY-MM-DD HH:MM:SS with N (3, 5, or 6) numbers (default = 5)

function str = datestr(t, n)
  
  if ~exists("n", "local")
    n = 5;
  end
  tlen = size(t, 2);
  str = "";
  
  select tlen
    case 1
      t = datevec(t);
      tlen = 6;
    case 3
    case 5
    case 6
  else
    error("T must have rows of length 1, 3, 5, or 6.")
  end
  
  t = trimdv(t);

  if n<tlen then
    t(:,n+1:$) = [];
  elseif n>tlen then
    t(:,$+1:n) = zeros(size(t,1),n-tlen);
  end  

  select n
    case 3
      str = msprintf("%4i-%02i-%02i\n", t(:, 1:3));
    case 5
      str = msprintf("%4i-%02i-%02i %02i:%02i\n", t(:, 1:5));
    case 6
      str = msprintf("%4i-%02i-%02i %02i:%02i:%02i\n", t(:, 1:6));
    else
      error("n must be 3, 5, or 6.")
  end

endfunction