Rename one particular column of a matrix in Stata - stata

Question

I am working on modyfinyg, renaming and arranging estimation results for final publication in Stata. What I have so far is:
sysuse auto, clear
* interaction model
gen int_mpg_mpg = mpg*mpg // generate interaction manually
qui regress price weight mpg int_mpg_mpg foreign
mat b=e(b) // store estimation results in matrix b
matrix list b // see the problem, colum 3 "int_mpg_mpg"
b[1,5]
weight mpg int_mpg_mpg foreign _cons
y1 3.0379251 -298.14637 5.8617627 3420.2156 -527.04589
* rename interaction with additional package erepost
local coln "b:weight b:mpg b:c.mpg#c.mpg b:foreign b:_cons"
mat colnames b= `coln'
capt prog drop replace_b
program replace_b, eclass
erepost b= b, rename
end
replace_b
eststo my_model
esttab my_model, label
This gives a nice version of the interaction term:
------------------------------------
(1)
Price
------------------------------------
b
Weight (lbs.) 3.038***
(3.84)
Mileage (mpg) -298.1
(-0.82)
Mileage (mpg) # Mi~) 5.862
(0.90)
Car type 3420.2***
(4.62)
Constant -527.0
(-0.08)
------------------------------------
Observations 74
------------------------------------
But imagine that I have many more models and variables. Then it becomes very unhandy to list all variables, all interactions etc. in this local coln
local coln "b:weight b:mpg b:c.mpg#c.mpg b:foreign b:_cons"
mat colnames b= `coln'
I am trying to only fix particular column names in the estimation matrix:
local colfix "b:c.mpg#c.mpg"
mat colnames b[1,3]= `colfix'
How can I access a particular column of a matrix in Stata?

Answer 1

Your intended new name seems the same as the existing name.
I don't know a way to change individual column names, but this may help:
. matrix foo = J(3, 4, 42)
. matrix colname foo = frog toad DRAGON griffin
. mat li foo
foo[3,4]
frog toad DRAGON griffin
r1 42 42 42 42
r2 42 42 42 42
r3 42 42 42 42
. local colnames : colnames foo
. local colnames : subinstr local colnames "DRAGON" "newt", all
. matrix colname foo = `colnames'
. matrix li foo
foo[3,4]
frog toad newt griffin
r1 42 42 42 42
r2 42 42 42 42
r3 42 42 42 42
It's a modest exercise to make that into a subroutine. The bigger deal is whether there is a way to do this in the estout suite, wonderful commands I never use.