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v4.1:: Reparametrization of the exponential distribution. 

git-svn-id: https://www.dynare.org/svn/dynare/trunk@2418 ac1d8469-bf42-47a9-8791-bf33cf982152
time-shift
stepan 2009-02-16 10:31:50 +00:00
parent bce9aba538
commit e1b8fb9bc4
1 changed files with 6 additions and 6 deletions
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12
matlab/distributions/toolbox/exprnd.m
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@ -1,14 +1,14 @@
function rnd = exprnd(a)
% Random samples from the exponential distribution with expectation 1/a
% and variance (1/a)^2.
% Random samples from the exponential distribution with expectation a
% and variance a^2.
%
% INPUTS
% a [double] m*n matrix of positive parameters
%
% OUTPUT
% rnd [double] m*n matrix, independent draws from the exponential
% distribution rnd(j,j) has expectation 1/a(i,j) and
% variance (1/a(i,j))^2
% distribution rnd(j,j) has expectation a(i,j) and
% variance a(i,j)^2.
%
% ALGORITHM
% Inverse transform sampling.
@ -33,10 +33,10 @@ function rnd = exprnd(a)
%
% You should have received a copy of the GNU General Public License
% along with Dynare. If not, see <http://www.gnu.org/licenses/>.
if any(a(:)<1e-15)
if any(a(:)<0)
disp('exprnd:: The parameter of the exponential distribution has to be positive!')
error;
end
[m,n] = size(a);
uniform_variates = rand(m,n);
rnd = -log(uniform_variates)./a;
rnd = -log(uniform_variates).*a;