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*! version 1 03 January 2012
************************************************************************************************************
* gausshermite2 : Estimate an integral of the form : f(x,y)g(x,y/mu,Sigma)dxdy where g(x,y/mu,Sigma) is the distribution function
* of the bivariate normal distribution of mean mu and covariance matrix Sigma by Gauss Hermite quadratures
*
* Version 1: 03 January 2012
*
*
* Mohand Feddag, University of Nantes - France
* Mohand-Larbi.Feddag@univ-nantes.fr *
* News about this program : http://anaqol.free.fr
* FreeIRT Project : http://freeirt.free.fr
*
* Copyright 2012 Mohand Feddag
*
* This program 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 2 of the License, or
* (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
************************************************************************************************************
program define gausshermite2,rclass
version 11
syntax anything [, Mu(string) Sigma(string) Nodes(integer 12) Display]
tempfile gauss2
qui capture save `gauss2',replace
local save=0
if _rc==0 {
qui save `gauss2',replace
local save=1
}
if "`mu'"=="" {
tempname mu
matrix `mu'=[0,0]
}
if "`sigma'"=="" {
tempname sigma
matrix `sigma'=[1,0\0,1]
}
tokenize `anything'
drop _all
qui set obs `=`nodes'*`nodes''
tempname noeuds poids
qui ghquadm `nodes' `noeuds' `poids'
* Cholesky transformation for the covariance matrix sigma
matrix C=cholesky(`sigma')
*matrix list C
local line=1
qui gen x1=.
qui gen x2=.
qui gen poids1=.
qui gen poids2=.
forvalues i=1/`nodes' {
forvalues j=1/`nodes' {
qui replace x1=`noeuds'[1,`i'] *(sqrt(2)*C[1,1])+`mu'[1,1] in `line'
qui replace x2=`noeuds'[1,`i'] *(sqrt(2)*C[2,1])+`noeuds'[1,`j'] *(sqrt(2)*C[2,2])+`mu'[1,2] in `line'
qui replace poids1=`poids'[1,`i'] in `line'
qui replace poids2=`poids'[1,`j'] in `line'
local ++line
}
}
* Double somme du produit poids[i]*poids[j]*f(x1,x2) qui est affect<63> a la variable sum
qui gen f=poids1*poids2*(`1')/(_pi)
*list x1 x2 poids1 f (sqrt(2)*_pi)
qui su f
local sum=r(sum)
return scalar int=`sum'
if "`display'"!="" {
di in green "int_R^2 (`1')g(x1,x2/mu=`mu',Sigma=`Sigma')dx1dx2=" in yellow %12.8f `sum'
}
drop _all
if `save'==1 {
qui use `gauss2',clear
}
end