/usr/share/octave/site/m/vlfeat/toolbox/aib/vl_aib.m is in octave-vlfeat 0.9.17+dfsg0-6build1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 | % VL_AIB Agglomerative Information Bottleneck
% PARENTS = VL_AIB(PCX) runs Agglomerative Information Bottleneck
% (AIB) on the class-feature co-occurrence matrix PCX and returns a
% vector PARENTS representing the sequence of compressed AIB
% alphabets.
%
% PCX is the joint probability of the occurrence of the class label
% C and the feature value X. PCX has one row for each class label
% and one column for each feature value, non negative entires and
% sums to one. AIB iteratively merges the pair of feature values
% that decreases the mutual information I(X,C) the least. This
% compresses the alphabet of the discrete random variable X in such
% a way that the new variable is still informative about C.
%
% Merge operations are represented by a binary tree. The nodes of
% the tree correspond to the original feature values and any other
% value obtained by merging.
%
% The vector PARENTS represents the merge tree. The nodes are
% numbered in breadth-first order, starting from the leaves. The
% numbers associated to the tree leaves correspond to the original
% feature values (so the first leaf has number one and correspond to
% the first feature value). In total there are 2*M-1 nodes, where M
% is the number of feature values (the number of columns of
% PCX). The internal nodes are numbered according to the order in
% which AIB generates them. It is therefore possible to recover from
% the tree the state of the AIB algorithm at each step (see also
% VL_AIBCUT()). PARENTS is a UINT32 array with one element for each
% tree node storing the index of the parent node. The root parent is
% conventionally set to 1.
%
% Feature values with null probability (null columns of the PCX
% matrix) are ignored by the AIB algorithm and the corresponding
% entries in the PARENTS vectors are set to zero. Notice that this
% causes the root of the tree to have index smaller of 2*M-1
% (PARENTS has still 2*M-1 entries, but the last portion is
% zero-padded).
%
% Alternatively, the option ClusterNull can be used to assign the
% null probability values to a special value. The result is similar
% to pretending that the null probability nodes have indeed very
% small probability, uniform across categories.
%
% [PARENTS, COST] = VL_AIB(...) returns the values COST of the cost
% function being optimized by AIB (i.e. the mutual information
% I(X,C)). COST has M column. The first column is the initial value
% of the cost function. The others correspond to the cost after each
% of the M-1 merges. If less than M-1 merges are performed, the rest
% of the vector is filled with NaNs.
%
% VL_AIB() accepts the following options:
%
% Verbose::
% If specified, increase verbosity level.
%
% ClusterNull::
% If specified, do not signal null nodes; instead cluster them.
%
% See also: VL_AIBCUT(), VL_AIBHIST(), VL_AIBCUTHIST(),
% VL_AIBCUTPUSH(), VL_HELP().
% Copyright (C) 2007-12 Andrea Vedaldi and Brian Fulkerson.
% All rights reserved.
%
% This file is part of the VLFeat library and is made available under
% the terms of the BSD license (see the COPYING file).
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