Daniel@0: function CPD = root_CPD(bnet, self, val)
Daniel@0: % ROOT_CPD Make a conditional prob. distrib. which has no parameters.
Daniel@0: % CPD = ROOT_CPD(BNET, NODE_NUM, VAL)
Daniel@0: %
Daniel@0: % The node must not have any parents and is assumed to always be observed.
Daniel@0: % It is a way of modelling exogenous inputs to a model.
Daniel@0: % VAL is the value to which the root is clamped (default: [])
Daniel@0: 
Daniel@0: 
Daniel@0: if nargin==0
Daniel@0:   % This occurs if we are trying to load an object from a file.
Daniel@0:   CPD = init_fields;
Daniel@0:   CPD = class(CPD, 'root_CPD', generic_CPD(1));
Daniel@0:   return;
Daniel@0: elseif isa(bnet, 'root_CPD')
Daniel@0:   % This might occur if we are copying an object.
Daniel@0:   CPD = bnet;
Daniel@0:   return;
Daniel@0: end
Daniel@0: CPD = init_fields;
Daniel@0: 
Daniel@0: 
Daniel@0: if nargin < 3, val = []; end
Daniel@0: 
Daniel@0: ns = bnet.node_sizes;
Daniel@0: ps = parents(bnet.dag, self);
Daniel@0: if ~isempty(ps)
Daniel@0:   error('root CPDs should have no parents')
Daniel@0: end
Daniel@0: 
Daniel@0: CPD.self = self;
Daniel@0: CPD.val = val;
Daniel@0: CPD.sizes = ns(self);
Daniel@0: 
Daniel@0: clamped = 1;
Daniel@0: CPD = class(CPD, 'root_CPD', generic_CPD(clamped));
Daniel@0: 
Daniel@0: 
Daniel@0: %%%%%%%%%%%
Daniel@0: 
Daniel@0: function CPD = init_fields()
Daniel@0: % This ensures we define the fields in the same order 
Daniel@0: % no matter whether we load an object from a file,
Daniel@0: % or create it from scratch. (Matlab requires this.)
Daniel@0: 
Daniel@0: CPD.self = [];
Daniel@0: CPD.val = [];
Daniel@0: CPD.sizes = [];