Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / financial-0.4.0 / m2xdate.m

diff --git a/octave_packages/financial-0.4.0/m2xdate.m b/octave_packages/financial-0.4.0/m2xdate.m
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+## Copyright (C) 2008 Bill Denney <bill@denney.ws>
+##
+## 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} {exceldatenums =} m2xdate (datenums)
+## @deftypefnx {Function File} {exceldatenums =} m2xdate (datenums, convention)
+## @deftypefnx {Function File} {exceldatenums =} m2xdate (datenums, convention, "ExcelBug")
+##
+## Convert @var{datenums} from the internal date format to the format
+## used by Microsoft Excel.  If set to 0 (default, Excel for Windows),
+## @var{convention} specifies to use the Excel 1900 convention where Jan
+## 1, 1900 corresponds to Excel serial date number 1.  If set to 1
+## (Excel for Mac), @var{convention} specifies to use the Excel 1904
+## convention where Jan 1, 1904 corresponds to Excel serial date number
+## 0.
+##
+## Note that this does not take into account the Excel bug where 1900 is
+## considered to be a leap year unless you give the "ExcelBug" option.
+##
+## Excel does not represent dates prior to 1 January 1900 using this
+## format, so a warning will be issued if any dates preceed this date.
+##
+## @seealso{datenum, x2mdate}
+## @end deftypefn
+
+function dates = m2xdate (dates, convention, excelbug)
+
+  if nargin == 1
+       convention = 0;
+       excelbug = false();
+  elseif nargin == 2
+       excelbug = false();
+  elseif nargin == 3
+       excelbug = strcmpi(excelbug, "ExcelBug");
+  else
+       print_usage ();
+  endif
+
+  if convention == 0
+       adj = datenum(1900, 1, 1) - 2;
+  elseif convention == 1
+       adj = datenum(1904, 1, 1);
+  endif
+
+  if excelbug
+       datemask = (dates < datenum(1900, 3, 1));
+       dates(datemask) = dates(datemask) - 1;
+  endif
+  dates = dates - adj;
+  if any (dates < 0)
+       warning ("Negative date found, this will not work within MS Excel.")
+  endif
+
+endfunction
+
+## Tests
+%!assert(m2xdate(datenum(2008, 1, 1)), 39448)
+%!assert(m2xdate(datenum(2007:2008, 1, 1)), [39083 39448])
+%!assert(m2xdate(datenum(1900, 1, 1)), 2)
+%!assert(m2xdate(datenum(1900, 1, 1), 0, "ExcelBug"), 1)
+%!assert(m2xdate(datenum(1904, 1, 1), 1), 0)
+