calc_LLt_prior

 LLt = calc_LLt_prior( data0, inv_model )
 CALC_LLt_PRIOR: calculate image regularization prior
   L*L' (which is an estimate of the inverse of the covariance in time)

   Typically, the image prior is matrix n_frames x n_frames of the
   normalized a priori cross-correlation between measurement frames
   where frames are a set of measurements taken at nearly the same time
 
 calc_LLt_prior can be called as
    LLt_prior= calc_LLt_prior( data0, ... )

 and will call the function inv_model.LLt_prior
 parameters to LLt_prior should be passed in the field
 inv_model.LLt_prior_function_name.parameters

 If inv_model.LLt_prior is a matrix, calc_LLt_prior will return that matrix,

 LLt_prior    the calculated LLt regularization prior
 inv_model    is an inv_model structure

 If a function to calculate LLt_prior is not provided,
 LLt = L_prior * L_prior';

0001 function LLt_prior = calc_LLt_prior( data0, inv_model )
0002 % LLt = calc_LLt_prior( data0, inv_model )
0003 % CALC_LLt_PRIOR: calculate image regularization prior
0004 %   L*L' (which is an estimate of the inverse of the covariance in time)
0005 %
0006 %   Typically, the image prior is matrix n_frames x n_frames of the
0007 %   normalized a priori cross-correlation between measurement frames
0008 %   where frames are a set of measurements taken at nearly the same time
0009 %
0010 % calc_LLt_prior can be called as
0011 %    LLt_prior= calc_LLt_prior( data0, ... )
0012 %
0013 % and will call the function inv_model.LLt_prior
0014 % parameters to LLt_prior should be passed in the field
0015 % inv_model.LLt_prior_function_name.parameters
0016 %
0017 % If inv_model.LLt_prior is a matrix, calc_LLt_prior will return that matrix,
0018 %
0019 % LLt_prior    the calculated LLt regularization prior
0020 % inv_model    is an inv_model structure
0021 %
0022 % If a function to calculate LLt_prior is not provided,
0023 % LLt = L_prior * L_prior';
0024 
0025 % (C) 2017 Alistair Boyle. License: GPL version 2 or version 3
0026 % $Id: calc_LLt_prior.m 5720 2018-03-28 11:57:45Z aadler $
0027 
0028 if isfield(inv_model,'LLt_prior')
0029    if isnumeric(inv_model.LLt_prior)
0030       LLt_prior = inv_model.LLt_prior;
0031    else
0032       try inv_model.LLt_prior = str2func(inv_model.LLt_prior); end
0033       LLt_prior= eidors_cache( inv_model.LLt_prior, inv_model );
0034    end
0035 elseif isfield(inv_model,'L_prior')
0036    LLt_prior = eidors_cache(@calc_from_L_prior, inv_model, 'calc_LLt_prior');
0037 else
0038    error('calc_LLt_prior: neither L_prior nor LLt_prior provided');
0039 end
0040 
0041 function LLt_prior = calc_from_L_prior(inv_model)
0042 
0043    % The user has provided an R prior. We can use this to
0044    % calculate LLt= L*L';
0045    if isnumeric(inv_model.L_prior)
0046       L = inv_model.L_prior;
0047    else
0048       try inv_model.L_prior = str2func(inv_model.L_prior); end
0049       L= eidors_cache( inv_model.L_prior, inv_model );
0050    end
0051 
0052    LLt_prior = L*L';