How can I stack equations using estout? - stata

Question

I am creating a summary statistics table using the community-contributed command estout.
The code looks like this:
sysuse auto, clear
eststo clear
eststo: estpost ttest price mpg weight headroom trunk if rep78 ==3, by(foreign)
eststo: estpost ttest price mpg weight headroom trunk if rep78 ==4, by(foreign)
estout, cells("mu_1 mu_2 b(star)")
The result looks as follows:
--------------------------------------------------------------------------------------------
est1 est2
mu_1 mu_2 b mu_1 mu_2 b
--------------------------------------------------------------------------------------------
price 6607.074 4828.667 1778.407 5881.556 6261.444 -379.8889
mpg 19 23.33333 -4.333333 18.44444 24.88889 -6.444444**
weight 3442.222 2010 1432.222*** 3532.222 2207.778 1324.444***
headroom 3.222222 2.666667 .5555556 3.444444 2.5 .9444444*
trunk 15.59259 12.33333 3.259259 16.66667 10.33333 6.333333**
--------------------------------------------------------------------------------------------
I would like to know how I could stack est1 and est2 on top of each other.

Answer 1

The command estout cannot automatically stack results from stored estimates. Consequently, the use of eststo is redundant. In this case, the easiest way to obtain the desired output is to simply create two matrices with the results and stack one on top of the other.
For example:
sysuse auto, clear
matrix A = J(5, 3, .)
local i 0
foreach var of varlist price mpg weight headroom trunk {
local ++i
ttest `var' if rep78 == 3, by(foreign)
matrix A[`i', 1] = r(mu_1)
matrix A[`i', 2] = r(mu_2)
matrix A[`i', 3] = r(mu_1) - r(mu_2)
local matnamesA `matnamesA' "rep78==3:`var'"
}
matrix rownames A = `matnamesA'
matrix B = J(5, 3, .)
local i 0
foreach var of varlist price mpg weight headroom trunk {
local ++i
ttest `var' if rep78 == 4, by(foreign)
matrix B[`i', 1] = r(mu_1)
matrix B[`i', 2] = r(mu_2)
matrix B[`i', 3] = r(mu_1) - r(mu_2)
local matnamesB `matnamesB' "rep78==4:`var'"
}
matrix rownames B = `matnamesB'
matrix C = A \ B
esttab matrix(C), nomtitles collabels("mu_1" "mu_2" "diff")
---------------------------------------------------
mu_1 mu_2 diff
---------------------------------------------------
rep78==3
price 6607.074 4828.667 1778.407
mpg 19 23.33333 -4.333333
weight 3442.222 2010 1432.222
headroom 3.222222 2.666667 .5555556
trunk 15.59259 12.33333 3.259259
---------------------------------------------------
rep78==4
price 5881.556 6261.444 -379.8889
mpg 18.44444 24.88889 -6.444444
weight 3532.222 2207.778 1324.444
headroom 3.444444 2.5 .9444444
trunk 16.66667 10.33333 6.333333
---------------------------------------------------