Daniel@0: function net = glminit(net, prior)
Daniel@0: %GLMINIT Initialise the weights in a generalized linear model.
Daniel@0: %
Daniel@0: %	Description
Daniel@0: %
Daniel@0: %	NET = GLMINIT(NET, PRIOR) takes a generalized linear model NET and
Daniel@0: %	sets the weights and biases by sampling from a Gaussian distribution.
Daniel@0: %	If PRIOR is a scalar, then all of the parameters (weights and biases)
Daniel@0: %	are sampled from a single isotropic Gaussian with inverse variance
Daniel@0: %	equal to PRIOR. If PRIOR is a data structure similar to that in
Daniel@0: %	MLPPRIOR but for a single layer of weights, then the parameters are
Daniel@0: %	sampled from multiple Gaussians according to their groupings (defined
Daniel@0: %	by the INDEX field) with corresponding variances (defined by the
Daniel@0: %	ALPHA field).
Daniel@0: %
Daniel@0: %	See also
Daniel@0: %	GLM, GLMPAK, GLMUNPAK, MLPINIT, MLPPRIOR
Daniel@0: %
Daniel@0: 
Daniel@0: %	Copyright (c) Ian T Nabney (1996-2001)
Daniel@0: 
Daniel@0: errstring = consist(net, 'glm');
Daniel@0: if ~isempty(errstring);
Daniel@0:   error(errstring);
Daniel@0: end
Daniel@0: if isstruct(prior)
Daniel@0:   sig = 1./sqrt(prior.index*prior.alpha);
Daniel@0:   w = sig'.*randn(1, net.nwts); 
Daniel@0: elseif size(prior) == [1 1]
Daniel@0:   w = randn(1, net.nwts).*sqrt(1/prior);
Daniel@0: else
Daniel@0:   error('prior must be a scalar or a structure');
Daniel@0: end  
Daniel@0: 
Daniel@0: net = glmunpak(net, w);
Daniel@0: