--- /dev/null
+## Copyright (C) 2007 David Bateman
+##
+## This program 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 3 of the License, or (at your option) any later
+## version.
+##
+## This program 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
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} daysact (@var{d1})
+## @deftypefnx {Function File} {} daysact (@var{d1}, @var{d2})
+## Calculates the number of days between two dates. If the second date is not
+## given, calculate the number of days since 1-Jan-0000. The variables @var{d1}
+## and @var{d2} can either be strings or an @var{n}-row string matrix. If both
+## @var{d1} and @var{d2} are string matrices, then the number of rows must
+## match. An example of the use of @code{daysact} is
+##
+## @example
+## @group
+## daysact ("01-Jan-2007", ["10-Jan-2007"; "23-Feb-2007"; "23-Jul-2007"])
+## @result{} 9
+## 53
+## 203
+## @end group
+## @end example
+## @seealso{datenum}
+## @end deftypefn
+
+function days = daysact (d1, d2)
+ if (nargin == 1)
+ nr = size (d1, 1);
+ if (nr != 1)
+ days = zeros (nr,1);
+ for i = 1 : nr
+ days (i) = datenum (d1 (i,:));
+ endfor
+ else
+ days = datenum(d1);
+ endif
+ elseif (nargin == 2)
+ nr1 = size (d1, 1);
+ nr2 = size (d2, 1);
+ if (nr1 != nr2 && nr1 != 1 && nr2 != 1)
+ error ("daysact: size mismatch");
+ endif
+ if (nr1 == 1 && nr2 == 1)
+ days = datenum (d2) - datenum(d1);
+ elseif (nr1 == 1)
+ days = zeros (nr2, 1);
+ for i = 1 : nr2
+ days(i) = datenum (d2 (i,:)) - datenum (d1);
+ endfor
+ elseif (nr2 == 1)
+ days = zeros (nr1, 1);
+ for i = 1 : nr1
+ days(i) = datenum (d2) - datenum (d1 (i,:));
+ endfor
+ else
+ days = zeros (nr1, 1);
+ for i = 1 : nr1
+ days(i) = datenum (d2 (i, :)) - datenum (d1 (i,:));
+ endfor
+ endif
+ else
+ print_usage();
+ endif
+endfunction
+
+%!assert (daysact ("01-Jan-2007", ["10-Jan-2007"; "23-Feb-2007"; "23-Jul-2007"]),[9;53;203])