how to represent estimates for covariates using Mata

[Xuan Hui]

I have a regression model using discrete time hazard regression. And I wanted to study the effect of modifier A (binary) and factor B(linear spline with 5 knots, represents by “B?" in below), and the interaction between A and B (represents by "B?int?" below) to the outcome y. There was 3 follow-up timepoints, so fu1, fu2, fu3 were used in the discrete time model.

Therefore, the regression writes: cloglog y i.A B? B?int? fu1 fu2 fu3, nocon eform

Then I want to calculate the estimates for 100 points, and use these estimates to draw a graph. And my question is highlighted in red below: I wonder to represent the coefficients for fu1, fu2, fu3 in mata structure, should I use m0? To simply my question, how to represent estimates in mata for the “covariates”.

Here is the code I wrote:

set obs 100

mata:xw=st_data(.,”B?")
mata:xn=J(100,5,0)
mata:m0=J(100,1,0)
mata:m1=J(100,1,1)

mata:x0=(xw,m0,m0,xn,m0,m0,m0) // reference group
mata:x1=(xw,m0,m0,xw,m0,m0,m0) // group 1 in A, without main effect
mata:x2=(xw,m0,m1,xw,m0,m0,m0) // group 1 in A, with main effect
mata:x3=(xn,m0,m0,xw,m0,m0,m0) // group 1 interaction

Thank you very much!

[FernandoRios]

Hi Xuan,
If you are not set on using mata, I have recently shared a piece of code for a case like yours.
See the code below for an example:

ssc install f_able
webuse lbw, clear
 
 fgen age2=max(age-19,0)
 fgen age3=max(age-23,0)
 fgen age4=max(age-26,0)
 
 cloglog low c.(age age2 age3 age4)#smoke lwt i.race 
 f_able, nl(age2 age3 age4)
 margins smoke, at(age=(16(2)32)) nochain numerical plot

See the paper linked at the end that explains how the command works.
Fernando