Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / financial-0.4.0 / x2mdate.m

diff --git a/octave_packages/financial-0.4.0/x2mdate.m b/octave_packages/financial-0.4.0/x2mdate.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} {datenums =} x2mdate (exceldatenums)
+## @deftypefnx {Function File} {datenums =} x2mdate (exceldatenums, convention)
+## @deftypefnx {Function File} {datenums =} x2mdate (exceldatenums, convention, "ExcelBug")
+##
+## Convert @var{datenums} from the Microsoft Excel date format to the
+## format used by @code{datenum}.  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 = x2mdate (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 any (dates < 0)
+       warning ("Negative date found, this will not work within MS Excel.")
+  endif
+
+  if convention == 0
+       adj = datenum(1900, 1, 1) - 2;
+  elseif convention == 1
+       adj = datenum(1904, 1, 1);
+  endif
+
+  if excelbug
+       datemask = (dates < 61);
+       dates(datemask) = dates(datemask) + 1;
+  endif
+  dates = dates + adj;
+
+endfunction
+
+## Tests
+%!assert(x2mdate(39448), datenum(2008, 1, 1))
+%!assert(x2mdate([39083 39448]), datenum(2007:2008, 1, 1))
+%!assert(x2mdate(2), datenum(1900, 1, 1))
+%!assert(x2mdate(1, 0, "ExcelBug"), datenum(1900, 1, 1))
+%!assert(x2mdate(0, 1), datenum(1904, 1, 1))
+