--- a
+++ b/@dataframe/private/df_check_char_array.m
@@ -0,0 +1,52 @@
+function resu = df_check_char_array(x, nelem, required)
+
+  %# auxiliary function: pad a char array to some width
+
+  %% Copyright (C) 2009-2010 Pascal Dupuis <Pascal.Dupuis@uclouvain.be>
+  %%
+  %% This file is part of Octave.
+  %%
+  %% Octave is free software; you can redistribute it and/or
+  %% modify it under the terms of the GNU General Public
+  %% License as published by the Free Software Foundation;
+  %% either version 2, or (at your option) any later version.
+  %%
+  %% Octave is distributed in the hope that it will be useful,
+  %% but WITHOUT ANY WARRANTY; without even the implied
+  %% warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+  %% PURPOSE.  See the GNU General Public License for more
+  %% details.
+  %%
+  %% You should have received a copy of the GNU General Public
+  %% License along with Octave; see the file COPYING.  If not,
+  %% write to the Free Software Foundation, 59 Temple Place -
+  %% Suite 330, Boston, MA 02111-1307, USA.
+  
+  %#
+  %# $Id: df_check_char_array.m 852 2010-07-22 10:47:55Z dupuis $
+  %#
+  
+  if 2 == nargin, required = [nelem 1]; endif
+
+  if nelem < required(1),
+    error("Too many elements to assign");
+  endif
+
+  %# a zero-length element is still considered as a space by char
+  if isempty(x), x = ' '; endif 
+
+  if size(x, 1) < max(required(1), nelem)
+    %# pad vertically
+    dummy = repmat(' ', nelem-size(x, 1), 1);
+    resu = char(x, dummy);
+  else
+    resu = x;
+  endif
+      
+  if size(resu, 2) < required(2),
+    %# pad horizontally
+    dummy = repmat(' ', nelem, required(2)-size(resu, 2));
+    resu = horzcat(resu, dummy);
+  endif
+
+endfunction