# HG changeset patch
# User bill@denney.ws
# Date 1206643898 14400
# Node ID d448ac8a4874626adc655f26d03df5a01b222e0c
# Parent  ea2344c4140b7d12653430c0907cc98adb281d14
addtodate.m: new function

diff -r ea2344c4140b -r d448ac8a4874 scripts/ChangeLog
--- a/scripts/ChangeLog	Thu Mar 27 14:48:36 2008 -0400
+++ b/scripts/ChangeLog	Thu Mar 27 14:51:38 2008 -0400
@@ -1,5 +1,7 @@
 2008-03-27  Bill Denney  <bill@denney.ws>
 
+	* time/addtodate.m: New function.
+
 	* geometry/rectint.m: Vectorize and add more tests.
 
 2008-03-27  John W. Eaton  <jwe@octave.org>
diff -r ea2344c4140b -r d448ac8a4874 scripts/time/Makefile.in
--- a/scripts/time/Makefile.in	Thu Mar 27 14:48:36 2008 -0400
+++ b/scripts/time/Makefile.in	Thu Mar 27 14:51:38 2008 -0400
@@ -32,8 +32,8 @@
 INSTALL_PROGRAM = @INSTALL_PROGRAM@
 INSTALL_DATA = @INSTALL_DATA@
 
-SOURCES = asctime.m calendar.m clock.m ctime.m date.m datenum.m \
-  datestr.m datevec.m eomday.m etime.m is_leap_year.m now.m \
+SOURCES = addtodate.m asctime.m calendar.m clock.m ctime.m date.m \
+  datenum.m datestr.m datevec.m eomday.m etime.m is_leap_year.m now.m \
   weekday.m
 
 DISTFILES = $(addprefix $(srcdir)/, Makefile.in $(SOURCES))
diff -r ea2344c4140b -r d448ac8a4874 scripts/time/addtodate.m
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/time/addtodate.m	Thu Mar 27 14:51:38 2008 -0400
@@ -0,0 +1,111 @@
+## Copyright (C) 2008 Bill Denney
+##
+## 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 3 of the License, 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, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{d} =} addtodate (@var{d}, @var{q}, @var{f})
+## Add @var{q} amount of time (with units @var{f}) to the datenum, @var{d}.
+##
+## @var{f} must be one of "year", "month", "day", "hour", "minute", or
+## "second".
+## @seealso{datenum, datevec}
+## @end deftypefn
+
+## Author: Bill Denney <bill@denney.ws>
+
+function d = addtodate (d, q, f)
+
+  if (nargin != 3)
+    print_usage ();
+  elseif (! (ischar (f) && rows (f) == 1))
+    ## FIXME: enhance the function so that it works with cellstrs of the
+    ## same size as the output.
+    error ("addtodate: f must be a single row character string.")
+  endif
+
+  if (numel (d) == 1 && numel (q) > 1)
+    ## expand d to the size of q if d only has one element to make
+    ## addition later eaiser.
+    d = d.*ones (size (q));
+  endif
+
+  ## in case the user gives f as a plural, remove the s
+  if ("s" == f(end))
+    f(end) = [];
+  endif
+
+  if (any (strcmpi ({"year" "month"}, f)))
+    dtmp = datevec (d);
+    if (strcmpi ("year", f))
+      dtmp(:,1) += q(:);
+    elseif (strcmpi ("month", f))
+      dtmp(:,2) += q(:);
+      ## adjust the years and months if the date rolls over a year
+      dtmp(:,1) += floor ((dtmp(:,2)-1)/12);
+      dtmp(:,2) = mod (dtmp(:,2)-1, 12) + 1;
+    endif
+    dnew = datenum (dtmp);
+    ## make the output the right shape
+    if (numel (d) == numel (dnew))
+      d = reshape (dnew, size (d));
+    else
+      d = reshape (dnew, size (q));
+    endif
+  elseif (any (strcmpi ({"day" "hour" "minute" "second"}, f)))
+    mult = struct ("day", 1, "hour", 1/24, "minute", 1/1440, "second", 1/86400);
+    d += q.*mult.(f);
+  else
+    error ("addtodate: Invalid time unit: %s", f)
+  endif
+
+endfunction
+
+## tests
+%!shared d
+%!  d = datenum (2008, 1, 1);
+## Identity
+%!assert (addtodate (d, 0, "year"), d)
+%!assert (addtodate (d, 0, "month"), d)
+%!assert (addtodate (d, 0, "day"), d)
+%!assert (addtodate (d, 0, "hour"), d)
+%!assert (addtodate (d, 0, "minute"), d)
+%!assert (addtodate (d, 0, "second"), d)
+## Add one of each
+## leap year
+%!assert (addtodate (d, 1, "year"), d+366)
+%!assert (addtodate (d, 1, "month"), d+31)
+%!assert (addtodate (d, 1, "day"), d+1)
+%!assert (addtodate (d, 1, "hour"), d+1/24)
+%!assert (addtodate (d, 1, "minute"), d+1/1440)
+%!assert (addtodate (d, 1, "second"), d+1/86400)
+## substract one of each
+%!assert (addtodate (d, -1, "year"), d-365)
+%!assert (addtodate (d, -1, "month"), d-31)
+%!assert (addtodate (d, -1, "day"), d-1)
+%!assert (addtodate (d, -1, "hour"), d-1/24)
+%!assert (addtodate (d, -1, "minute"), d-1/1440)
+%!assert (addtodate (d, -1, "second"), d-1/86400)
+## rollover
+%!assert (addtodate (d, 12, "month"), d+366)
+%!assert (addtodate (d, 13, "month"), d+366+31)
+## multiple inputs and output orientation
+%!assert (addtodate ([d d], [1 13], "month"), [d+31 d+366+31])
+%!assert (addtodate ([d;d], [1;13], "month"), [d+31;d+366+31])
+%!assert (addtodate (d, [1;13], "month"), [d+31;d+366+31])
+%!assert (addtodate (d, [1 13], "month"), [d+31 d+366+31])
+%!assert (addtodate ([d;d+1], 1, "month"), [d+31;d+1+31])
+%!assert (addtodate ([d d+1], 1, "month"), [d+31 d+1+31])