Linear Combination of Coefficient

[Janys Ung]

Dear Statalists,

I'm trying to check if the beta coefficients retrieved from two separate regressions are significantly different. I'm using the `lincom' command and it works perfectly. But I couldn't save the degree of freedom (df). The manual shows that the df is stored in r(df), but I couldn't save it. Following is my code. I want to save it in Mata as I need to do the further computation in Mata later.

lincom [R5]SN - [R1]SN 
mata: a = st_numscalar("r(df)")

I would be very grateful if anyone could help me on this.

Thanks, Janys

[Phil Bromiley]

You might try putting r(df) into a local and then using that local in your mata statement. While this is probably inefficient, it sometimes works for me.

[Janys Ung]

Hi Phil Bromiley, many thanks for your solution!

Best, Janys