Hi,
I am new to the forum. I am working on conducting some statistical analysis in stata. I have couple of queries:

1. I am very confused in differentiating between centile, xtile and p in stata. I want to find the lower 5th percentile (quantile) of a variable for each panel ID that I have (by ID). please help me know the relevant code.

2. I am conducting quantile regression on a panel data set and I want to know the difference between "xtqreg" and "by panelID qreg". Also when I want to run the regression individually for each Panel ID that I have tried to do using xtreg, it doesnot accepts "by" option and gives the aggregate quantile regression results for the entire data-set and not just the individual firms or panel IDs.

3. Lastly, when I use "by panelID qreg" and want to output the results in asdoc, it doesnot considers sorting w.r..t "by panelID" rather only gives the aggregated regression result for the entire data-set. How can I output regression results using asdoc for individual firms using "by panelID" or "bysort PanelID"

Much Thanks
Aamina