function [ x, seed ] = normal ( dim_num, n, r, mu, seed ) %*****************************************************************************80 % %% NORMAL creates normally distributed points. % % Discussion: % % The multivariate normal distribution for the DIM_NUM dimensional vector X % has the form: % % pdf(X) = (2*pi*det(V))**(-DIM_NUM/2) % * exp(-0.5*(X-MU)'*inverse(V)*(X-MU)) % % where MU is the mean vector, and V is a positive definite symmetric % matrix called the variance-covariance matrix. % % This routine requires that the user supply the upper triangular % Cholesky factor R, which has the property that % % V = R' * R % % This factorization always exists if V is actually symmetric and % positive definite. This factorization can be computed by the % routine DPO_FA. % % The user also supplies the mean vector MU. % % Licensing: % % This code is distributed under the GNU LGPL license. % % Modified: % % 05 August 2005 % % Author: % % John Burkardt % % Parameters: % % Input, integer DIM_NUM, the dimension of the space. % % Input, integer N, the number of points. % % Input, real R(DIM_NUM,DIM_NUM), the upper triangular % Cholesky factor of the variance-covariance matrix. % % Input, real MU(DIM_NUM), the mean vector. % % Output, real X(DIM_NUM,N), the points. % % % Get a matrix of normal data. % [ x(1:dim_num,1:n), seed ] = r8mat_normal_01 ( dim_num, n, seed ); % % Compute R' * X. % We actually carry out this computation in the equivalent form X' * R. % for j = 1 : n x(1:dim_num,j) = mu(1:dim_num)' ... + ( r(1:dim_num,1:dim_num) )' * x(1:dim_num,j); end return end