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Diffstat (limited to 'sourcecodes/bnt-master/netlab3.3/demgpot.m')
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diff --git a/sourcecodes/bnt-master/netlab3.3/demgpot.m b/sourcecodes/bnt-master/netlab3.3/demgpot.m new file mode 100644 index 00000000..c859fd0b --- /dev/null +++ b/sourcecodes/bnt-master/netlab3.3/demgpot.m @@ -0,0 +1,29 @@ +function g = demgpot(x, mix) +%DEMGPOT Computes the gradient of the negative log likelihood for a mixture model. +% +% Description +% This function computes the gradient of the negative log of the +% unconditional data density P(X) with respect to the coefficients of +% the data vector X for a Gaussian mixture model. The data structure +% MIX defines the mixture model, while the matrix X contains the data +% vector as a row vector. Note the unusual order of the arguments: this +% is so that the function can be used in DEMHMC1 directly for sampling +% from the distribution P(X). +% +% See also +% DEMHMC1, DEMMET1, DEMPOT +% + +% Copyright (c) Ian T Nabney (1996-2001) + +% Computes the potential gradient + +temp = (ones(mix.ncentres,1)*x)-mix.centres; +temp = temp.*(gmmactiv(mix,x)'*ones(1, mix.nin)); +% Assume spherical covariance structure +if ~strcmp(mix.covar_type, 'spherical') + error('Spherical covariance only.') +end +temp = temp./(mix.covars'*ones(1, mix.nin)); +temp = temp.*(mix.priors'*ones(1, mix.nin)); +g = sum(temp, 1)/gmmprob(mix, x); \ No newline at end of file |