stokes_reduced_data_subset.m

function reduced_data_subset = stokes_reduced_data_subset(model, reduced_data)
%function reduced_data_subset = stokes_reduced_data_subset(model, reduced_data)
%
% copying ...
% switch to lin_stat_ .. later ?


reduced_data_subset = reduced_data;

if reduced_data.N ~= model.N
    
    % extract correct N-sized submatrices and subvectors from reduced_data
    if model.N > reduced_data.N
        error('N too large for current size of reduced basis!');
    end
    
    N = model.N;
    
    if strcmp(model.RB_error_indicator, 'estimator') && model.has_nonlinearity
        error('stokes:reduced_data_subset:this is not supported.');
        % residual components are to be computed again.
    end
    
    if isfield(reduced_data, 'AN_comp')
        reduced_data_subset.AN_comp   = ...
            subblock_sequence(reduced_data.AN_comp, 1:N, 1:N);
    end
    
    if isfield(reduced_data, 'fN_comp')
        reduced_data_subset.fN_comp = subblock_sequence(reduced_data.fN_comp, 1:N);
    end
    
    if isfield(reduced_data, 'KN')
        reduced_data_subset.KN = reduced_data.KN(1:N, 1:N);
    end
    
    Q_f = length(reduced_data_subset.fN_comp);
    Q_a = length(reduced_data_subset.AN_comp);
    ind = reduced_data.res_onb_ind < (Q_f+N*Q_a);
    reduced_data_subset.G = reduced_data.G(ind,1:(Q_f+N*Q_a));
    
    reduced_data_subset.N = N;
    
end