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# st: RE: Create a row matrix with weighted frequencies from various dummy variables

 From Nick Cox To "'statalist@hsphsun2.harvard.edu'" Subject st: RE: Create a row matrix with weighted frequencies from various dummy variables Date Fri, 1 Jul 2011 11:58:57 +0100

```Note that the reference to -tabcount- should have been explained. But you don't need -tabcount-.

clear
set seed 10235
set obs 1000
forv i=1/20 {
gen d`i' = round(uniform())
}
forv j=1/5 {
gen z`j' = round(uniform())
}
generate wt = uniform()

matrix count = J(1, 100, .)
local k = 0
qui forv i = 1/20 {
forv j = 1/5 {
su wt if d`i' == 1 & z`j' == 1, meanonly
matrix count[1, `++k'] = r(sum)
}
}

Nick
n.j.cox@durham.ac.uk

Nikolaos Kanellopoulos

I have two sets of dummy variables (say d1,...,d20 and z1,...,z5) and I want to
create a 1x100 matrix where each element will be the weighted frequency for each
combination between each d-variable and each z-variable when both equal 1 (lets
say something like this [d1=1&z1=1(wt),
d1=1&z2=1(wt),...,d200=1&z4=1(wt),d200=1&z5=1(wt)].

My thought is to use the following:
********************************************************************
clear *
set seed 10235
drop _all
set obs 1000
/*Generate data*/
forv i=1/20 {
gen d`i' = round(uniform())
}
forv i=1/5 {
gen z`i' = round(uniform())
}
generate wt = uniform()
/*generate 100 variables=1 if both dummy vars=1*/
forv i=1/20 {
forv j=1/5  {
ta d`i' if d`i'==1 & z`j'==1 , gen(d`i'z`j')
}
}
/*Check no missing variables and replace with zero if missing*/
forv i=1/20 {
forv j=1/5 {
capt su d`i'z`j'1
if _rc!=0 {
gen d`i'z`j'1=0
}
}
}
/*use tabcount to create 1x1 matrix with frequency for each dz combination*/
forv i=1/20 {
forv j=1/5 {
tabcount d`i'z`j'1 [iw=wt], v1(1) matrix(d`i'z`j')
}
}
/*Put in a 1x100 matrix*/
mat D1=d1z1
forv i=2/5 {
mat D1=D1,d1z`i'
}
mat D=D1
forv i=2/20 {
forv j=1/5{
mat D=D,d`i'z`j'
}
}
/*Round the elements of D*/
mata
d=st_matrix("D")
D=round(d)
st_matrix("D2",D)
end
********************************************************************

Is there a more efficient way to do this? Any suggestion is welcome.

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```