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% @STK_SAMPCRIT_EQI/FEVAL [overload base function]
%
% See also: feval
% Copyright Notice
%
% Copyright (C) 2016, 2017, 2020 CentraleSupelec
% Copyright (C) 2016 EDF R&D
%
% Authors: Tom Assouline, Florent Autret & Stefano Duhamel (for EDF R&D)
% Julien Bect <julien.bect@centralesupelec.fr>
% Copying Permission Statement
%
% This file is part of
%
% STK: a Small (Matlab/Octave) Toolbox for Kriging
% (https://github.com/stk-kriging/stk/)
%
% STK is free software: you can redistribute it and/or modify it under
% the terms of the GNU General Public License as published by the Free
% Software Foundation, either version 3 of the License, or (at your
% option) any later version.
%
% STK is distributed in the hope that it will be useful, but WITHOUT
% ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
% or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
% License for more details.
%
% You should have received a copy of the GNU General Public License
% along with STK. If not, see <http://www.gnu.org/licenses/>.
function [EQI, zp] = feval (crit, x, tau2)
zp = stk_predict (crit.model, x);
zp_mean = zp.mean;
zp_std = sqrt (zp.var);
if nargin < 3
% If tau2 is missing, compute tau2 assuming that a batch of size
% crit.point_batch_size will be made at the selected evaluation point.
% Otherwise, use the value of tau2 provided as an input argument. Note
% that the value of crit.point_batch_size is ignored in this second case.
if stk_isnoisy (crit.model)
if isa (crit.point_batch_size, 'function_handle')
n = stk_get_sample_size (crit.model);
pbs = feval (crit.point_batch_size, x, n);
else
pbs = crit.point_batch_size;
end
prior_model = get (crit.model, 'prior_model');
tau2 = (exp (prior_model.lognoisevariance)) / pbs;
else
tau2 = 0;
end
end
tmp = (zp_std .^ 2) ./ (tau2 + zp_std .^ 2);
tmp(zp_std == 0) = 0.0;
quantile_moy = zp_mean + crit.quantile_value * (sqrt (tau2 .* tmp));
quantile_var = (zp_std .^ 2) .* tmp;
EQI = stk_sampcrit_ei_eval ( ...
quantile_moy, sqrt (quantile_var), crit.current_minimum);
end % function
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