dynare/matlab/missing/stats/+gamrnd/berman.m

49 lines
1.3 KiB
Matlab

function g = berman(a,b)
% Returns gamma variates, see Devroye (1986) page 418.
%
% INPUTS
% - a [double] n*1 vector, first hyperparameter.
% - b [double] n*1 vector, second hyperparameter.
%
% OUTPUTS
% - g [double] n*1 vector, gamma variates.
% Copyright © 2006-2018 Dynare Team
%
% This file is part of Dynare.
%
% Dynare 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.
%
% Dynare 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 Dynare. If not, see <https://www.gnu.org/licenses/>.
nn = length(a);
mm = nn;
aa = 1./a ;
cc = 1./(1-a) ;
INDEX = 1:mm;
index = INDEX;
UV = NaN(nn,2);
X = NaN(nn,1);
Y = NaN(nn,1);
while mm
UV(index,:) = rand(mm,2);
X(index) = UV(index,1).^aa(index);
Y(index) = UV(index,2).^cc(index);
index = index(X(index)+Y(index)>1);
mm = length(index);
end
Z = gamrnd(2*ones(nn,1), ones(nn,1));
g = (Z.*X).*b ;