What does two consecutive hash marks mean?

[Phuc Nguyen]

From reading the function in xtdidregress released for Stata 17 as described here. On the page 11 and 12, I saw a description and regression as below:

Suppose we have a panel dataset with 10 time points, denoted by t1, where a treatment has taken place between t1 = 5 and t1 = 6. We have a set of covariates, x1 and x2, and an outcome, y1

I am wondering what does the two hash marks mean in this case. From my point if we want to list two set of variables c1 and c2, we should put

$c1 $c2

Best regards.

[Maxence Morlet]

two consecutive # tell stata you want to include each variable individually and their interaction

[Joseph Coveney]

It's shorthand for two continuous predictors and their interaction, that is:

c.x1 c.x2 c.x1#c.x2

At Stata's command line, type

help fvvarlist

for more information.

[Phuc Nguyen]

Dear Maxence Morlet and Joseph Coveney

Thank you so much, I got the point.