logprior.m.txt

这是马尔可夫-蒙特卡罗算法的MATLAB源程序.

function [lpv,b] = logPrior(p,m,lic)
% [lpv,b] = logPrior(p,m,lic)
% [lpv,b] = logPrior(DR,m,lic)
% Calculate log of prior for state p, or matrix of resistances DR, given model m
% need to supply lic for cell-based prior
%
% Optionally returns b, a vector of booleans over nodes or cells that is true
% if the node/cell has different valued resistors on the node/cell.

% Colin Fox, 11 Jan 2003.
% cell-based prior added 28 Jan 2003

cell = 1;                          % 0=node based prior, 1=cell based prior

if isstruct(p)
    DR = p.DR;
else
    DR = p;
end

[nn,mm] = size(DR);                % nn is the number of nodes
nr = length(m.Resistances);        % number of allowable resistances

if cell==0
    % node based prior
    R = DR + DR';                  % symmetric matrix of resistances
    ni = zeros(nr,nn);             % initialise number of each type
    for it = 1:nr                  % loop over types
        ni(it,:) = sum(R==m.Resistances(it)); % number of type cr at each node
    end
else
    % cell based prior
%    cr = zeros(size(lic));         % resistors on each cell
%    cr(:)=full(DR(lic(:)));        % each row is resistors round cell
%   cr = cr';
    cr = DR(lic);
    ni = zeros(nr,size(lic,2));    % initialize number of each type
    for it = 1:nr                  % loop over types
        ni(it,:) = sum(cr==m.Resistances(it)); % number of type it round each cell
    end
end

dv = sum(ni).^2 - sum(ni.^2);      % number of differences at each node or cell
sv = sum(ni.^2) - sum(ni);         % number the same at each nodeor cell

if nargout > 1
    b = dv ~= 0;
end

lpv = m.Theta*sum(sv);             % sum is over nodes or cells
disp(lpv)