Question on option "xline" for twoway graphs (plot: line)

[Ross Bundy]

Dear Forum,

I try to add a vertical line to my illustration [twoway graph (plot: line)]. The x-axis is my time variable from a panel dataset, which was computed in the following way:

generate yearmo = ym(year, month)
format yearmo %tm

I now try to use the xline option to insert a vertical line on the x-axis, but Stata is not accepting any specified date e.g. 2015m3. I assume I am entering the date in a wrong format, but this is how the dates are specified when I look at the dataset. When I enter a random number e.g. 100, Stata accepts the option but I don't see a line.

Thank you very much in advance for your advice!

Regards,

Ross

[Nick Cox]

The monthly date shown as 2015m3 is "really" 662. Your seeing anything else is a consequence of your assigned display format.

Conversely 100 as a monthly date was in 1968 and is ignored as (presumably) outside the range of your data.

There are various ways to get what you want.

Here is a demonstration you can try:

clear

di %tm 100
di ym(2015, 3)
di %tm 662

set obs 12
gen y = 42
gen date = ym(2015, _n)
format date %tm
line y date, xli(`=tm(2015m3)')
line y date, xli(`=ym(2015,3)')

[Ross Bundy]

Hi Nick, thank you! Using xline(`=tm(2008m9)') instead of simply 2015m3 worked!

[Nick Cox]

Modulo the fact that September 2008 was not March 2015....