what does [fweight=weight] mean?

[Phuc Nguyen]

When studying propensity score matching, I found a website show some code explaing how the code work
However, there is a line of code that I still not yet understood

reg y x1 x2 t [fweight=weight]

I am wondering what does the option [fweight=weight] mean. Whether it means that if the weight=5 (the control being matched 5 times). So when putting this unit to the regression, that unit will be duplicate 5 times?

Thanks in advance.

[Clyde Schechter]

Yes, if an observation has weight = 5, then in the regression, there will be "5 copies" of that observation included in the regressions. Stata does not actually expand the data set with extra copies of the variable to do this. But it is as if there were 5 such observations in the data set. The f in fweight stands for frequency.

[Phuc Nguyen]

Thank you Clyde Schechter , this explanation makes sense to me