--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m-toolbox/classes/@smodel/diff.m	Wed Nov 23 19:22:13 2011 +0100
@@ -0,0 +1,126 @@
+% DIFF implements differentiation operator for smodel objects.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%
+% DESCRIPTION: DIFF implements differentiation operator for smodel objects.
+%
+% CALL:        obj = diff(mdl, var)
+%              obj = mdl.diff(var)
+%              obj = mdl.diff(plist('var', var))
+%
+% <a href="matlab:utils.helper.displayMethodInfo('smodel', 'diff')">Parameters Description</a>
+%
+% VERSION:     $Id: diff.m,v 1.12 2011/04/08 08:56:29 hewitson Exp $
+%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+function varargout = diff(varargin)
+  
+  % Settings
+  operatorName = 'diff';
+  
+  % Check if this is a call for parameters
+  if utils.helper.isinfocall(varargin{:})
+    varargout{1} = getInfo(varargin{3});
+    return
+  end
+  
+  % Check if the method was called by another method
+  callerIsMethod = utils.helper.callerIsMethod;
+  
+  % Collect input variable names
+  in_names = cell(size(varargin));
+  for ii = 1:nargin,in_names{ii} = inputname(ii);end
+  
+  % Collect all smodels and plists
+  [mdl, smodel_invars, rest] = utils.helper.collect_objects(varargin(:), 'smodel', in_names);
+  [pl, pl_invars, rest]      = utils.helper.collect_objects(rest(:), 'plist', in_names);
+  
+  if numel(mdl) ~= 1
+    error('### diff only accepts one input smodel.');
+  end
+  
+  % Decide on a deep copy or a modify
+  dmdl = copy(mdl, nargout);
+  
+  % Combine input plists and default PLIST
+  pl = parse(pl, getDefaultPlist());
+  
+  % Select the variable to differentiate with respect to and the order:
+  [var, n, pl] = utils.helper.process_smodel_diff_options(pl, rest);
+  
+  % Check the variable
+  if isempty(var)
+    var = mdl.xvar;
+    if iscell(var)
+      var = var{1};
+    end
+  end
+  
+  if isempty(var)
+    error(['### Please specify a variable to differentiate with respect to, ' ...
+      'or set the xvar properties of the model(s)!']);
+  end
+  
+  % If the method was called by another method, we do not need to set history.
+  % As such, the info object can be empty
+  if callerIsMethod
+    infoObj = [];
+  else
+    infoObj = getInfo('None');
+  end
+  
+  % Apply the method to the model
+  dmdl.sop(callerIsMethod, smodel_invars, operatorName, {var, n}, pl, infoObj);
+  
+  % Set units
+  if strcmp(var, mdl.xvar)
+    setYunits(dmdl, dmdl.yunits ./ dmdl.xunits);
+  end
+
+  % Set output
+  varargout{1} = dmdl;
+
+end
+
+%--------------------------------------------------------------------------
+% Get Info Object
+%--------------------------------------------------------------------------
+function ii = getInfo(varargin)
+  
+  if nargin == 1 && strcmpi(varargin{1}, 'None')
+    sets = {};
+    pls  = [];
+  else
+    sets = {'Default'};
+    pls  = getDefaultPlist();
+  end
+  % Build info object
+  ii = minfo(mfilename, 'smodel', 'ltpda', utils.const.categories.op, '$Id: diff.m,v 1.12 2011/04/08 08:56:29 hewitson Exp $', sets, pls);
+  ii.setArgsmin(1);
+end
+
+%--------------------------------------------------------------------------
+% Get Default Plist
+%--------------------------------------------------------------------------
+function plout = getDefaultPlist()
+  persistent pl;
+  if ~exist('pl', 'var') || isempty(pl)
+    pl = buildplist();
+  end
+  plout = pl;
+end
+
+function pl = buildplist()
+  pl = plist();
+  
+  % Var
+  p = param({'var', ['Variable to differentiate with respect to.<br>' ...
+    'If left empty, the x variable of the model(s) will be used']}, paramValue.STRING_VALUE(''));
+  pl.append(p);
+  
+  % n
+  p = param({'n', 'Order of differentiation'}, {1, {1}, paramValue.OPTIONAL});
+  pl.append(p);
+end
+
+