comparison toolboxes/FullBNT-1.0.7/KPMstats/mixgauss_prob.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function [B, B2] = mixgauss_prob(data, mu, Sigma, mixmat, unit_norm)
+% EVAL_PDF_COND_MOG Evaluate the pdf of a conditional mixture of Gaussians
+% function [B, B2] = eval_pdf_cond_mog(data, mu, Sigma, mixmat, unit_norm)
+%
+% Notation: Y is observation, M is mixture component, and both may be conditioned on Q.
+% If Q does not exist, ignore references to Q=j below.
+% Alternatively, you may ignore M if this is a conditional Gaussian.
+%
+% INPUTS:
+% data(:,t) = t'th observation vector 
+%
+% mu(:,k) = E[Y(t) | M(t)=k] 
+% or mu(:,j,k) = E[Y(t) | Q(t)=j, M(t)=k]
+%
+% Sigma(:,:,j,k) = Cov[Y(t) | Q(t)=j, M(t)=k]
+% or there are various faster, special cases:
+%   Sigma() - scalar, spherical covariance independent of M,Q.
+%   Sigma(:,:) diag or full, tied params independent of M,Q. 
+%   Sigma(:,:,j) tied params independent of M. 
+%
+% mixmat(k) = Pr(M(t)=k) = prior
+% or mixmat(j,k) = Pr(M(t)=k | Q(t)=j) 
+% Not needed if M is not defined.
+%
+% unit_norm - optional; if 1, means data(:,i) AND mu(:,i) each have unit norm (slightly faster)
+%
+% OUTPUT:
+% B(t) = Pr(y(t)) 
+% or
+% B(i,t) = Pr(y(t) | Q(t)=i) 
+% B2(i,k,t) = Pr(y(t) | Q(t)=i, M(t)=k) 
+%
+% If the number of mixture components differs depending on Q, just set the trailing
+% entries of mixmat to 0, e.g., 2 components if Q=1, 3 components if Q=2,
+% then set mixmat(1,3)=0. In this case, B2(1,3,:)=1.0.
+
+
+
+
+if isvectorBNT(mu) & size(mu,2)==1
+  d = length(mu);
+  Q = 1; M = 1;
+elseif ndims(mu)==2
+  [d Q] = size(mu);
+  M = 1;
+else
+  [d Q M] = size(mu);
+end
+[d T] = size(data);
+
+if nargin < 4, mixmat = ones(Q,1); end
+if nargin < 5, unit_norm = 0; end
+
+%B2 = zeros(Q,M,T); % ATB: not needed allways
+%B = zeros(Q,T);
+
+if isscalarBNT(Sigma)
+  mu = reshape(mu, [d Q*M]);
+  if unit_norm % (p-q)'(p-q) = p'p + q'q - 2p'q = n+m -2p'q since p(:,i)'p(:,i)=1
+    %avoid an expensive repmat
+    disp('unit norm')
+    %tic; D = 2 -2*(data'*mu)'; toc 
+    D = 2 - 2*(mu'*data);
+    tic; D2 = sqdist(data, mu)'; toc
+    assert(approxeq(D,D2)) 
+  else
+    D = sqdist(data, mu)';
+  end
+  clear mu data % ATB: clear big old data
+  % D(qm,t) = sq dist between data(:,t) and mu(:,qm)
+  logB2 = -(d/2)*log(2*pi*Sigma) - (1/(2*Sigma))*D; % det(sigma*I) = sigma^d
+  B2 = reshape(exp(logB2), [Q M T]);
+  clear logB2 % ATB: clear big old data
+  
+elseif ndims(Sigma)==2 % tied full
+  mu = reshape(mu, [d Q*M]);
+  D = sqdist(data, mu, inv(Sigma))';
+  % D(qm,t) = sq dist between data(:,t) and mu(:,qm)
+  logB2 = -(d/2)*log(2*pi) - 0.5*logdet(Sigma) - 0.5*D;
+  %denom = sqrt(det(2*pi*Sigma));
+  %numer = exp(-0.5 * D);
+  %B2 = numer/denom;
+  B2 = reshape(exp(logB2), [Q M T]);
+  
+elseif ndims(Sigma)==3 % tied across M
+  B2 = zeros(Q,M,T);
+  for j=1:Q
+    % D(m,t) = sq dist between data(:,t) and mu(:,j,m)
+    if isposdef(Sigma(:,:,j))
+      D = sqdist(data, permute(mu(:,j,:), [1 3 2]), inv(Sigma(:,:,j)))';
+      logB2 = -(d/2)*log(2*pi) - 0.5*logdet(Sigma(:,:,j)) - 0.5*D;
+      B2(j,:,:) = exp(logB2);
+    else
+      error(sprintf('mixgauss_prob: Sigma(:,:,q=%d) not psd\n', j));
+    end
+  end
+  
+else % general case
+  B2 = zeros(Q,M,T);
+  for j=1:Q
+    for k=1:M
+      %if mixmat(j,k) > 0
+      B2(j,k,:) = gaussian_prob(data, mu(:,j,k), Sigma(:,:,j,k));
+      %end
+    end
+  end
+end
+
+% B(j,t) = sum_k B2(j,k,t) * Pr(M(t)=k | Q(t)=j) 
+
+% The repmat is actually slower than the for-loop, because it uses too much memory
+% (this is true even for small T).
+
+%B = squeeze(sum(B2 .* repmat(mixmat, [1 1 T]), 2));
+%B = reshape(B, [Q T]); % undo effect of squeeze in case Q = 1
+  
+B = zeros(Q,T);
+if Q < T
+  for q=1:Q
+    %B(q,:) = mixmat(q,:) * squeeze(B2(q,:,:)); % squeeze chnages order if M=1
+    B(q,:) = mixmat(q,:) * permute(B2(q,:,:), [2 3 1]); % vector * matrix sums over m
+  end
+else
+  for t=1:T
+    B(:,t) = sum(mixmat .* B2(:,:,t), 2); % sum over m
+  end
+end
+%t=toc;fprintf('%5.3f\n', t)
+
+%tic
+%A = squeeze(sum(B2 .* repmat(mixmat, [1 1 T]), 2));
+%t=toc;fprintf('%5.3f\n', t)
+%assert(approxeq(A,B)) % may be false because of round off error