Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / miscellaneous-1.1.0 / units.m

diff --git a/octave_packages/miscellaneous-1.1.0/units.m b/octave_packages/miscellaneous-1.1.0/units.m
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+## Copyright (C) 2005 Carl Osterwisch <osterwischc@asme.org>
+##
+## 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} {} units (@var{fromUnit}, @var{toUnit})
+## @deftypefnx {Function File} {} units (@var{fromUnit}, @var{toUnit}, @var{x})
+## Return the conversion factor from @var{fromUnit} to @var{toUnit} measurements.
+##
+## This is an octave interface to the @strong{GNU Units} program which comes
+## with an annotated, extendable database defining over two thousand 
+## measurement units.  See @code{man units} or 
+## @url{http://www.gnu.org/software/units} for more information.
+## If the optional argument @var{x} is supplied, return that argument
+## multiplied by the conversion factor.  Nonlinear conversions
+## such as Fahrenheit to Celsius are not currently supported.  For example, to 
+## convert three values from miles per hour into meters per second:
+##
+## @example
+## units ("mile/hr", "m/sec", [30, 55, 75])
+## ans =
+##
+##   13.411  24.587  33.528
+## @end example
+## @end deftypefn
+
+function y = units(fromUnit, toUnit, x)
+    if 2 > nargin || 3 < nargin || !ischar(fromUnit) || !ischar(toUnit)
+        print_usage;
+    endif
+
+    [status, rawoutput] = system(sprintf('units "%s" "%s"', fromUnit, toUnit), 1);
+    (0 == status) || error([rawoutput,
+        'Verify that GNU units is installed in the current path.']);
+    
+    i = index(rawoutput, "*");
+    j = index(rawoutput, "\n") - 1;
+    i && (i < j) || error('parsing units output "%s"', rawoutput);
+
+    exist("x", "var") || (x = 1);
+    eval(['y = x', rawoutput(i:j), ';'])
+endfunction
+
+%!demo
+%! a.value = 100; a.unit = 'lb';
+%! b.value =  50; b.unit = 'oz';
+%! c.unit = 'kg';
+%! c.value = units(a.unit, c.unit, a.value) + units(b.unit, c.unit, b.value)
+
+%!assert( units("in", "mm"), 25.4 )