Scatterplot of dates?

[Maisha Huq]

Hi All,

I'm using STATA 15.

My question is how do I convert and then format a datetime variable (current type: double, format: %tc) properly so I can create a scatterplot where both axes show certain mm/yy?

My code is below. Please let me know if I can provide better/additional info! Thank you so much

format firstr_birth %td
format secondr_birth %td
graph twoway scatter secondr_birth firstr_birth, ///
legend(off) mcolor(black) ///
ytitle("Date of first live birth during follow-up round") ///
xtitle("Date of first live birth at baseline")  ///
title("Plot of dates of first live birth as reported during baseline & follow-up rounds", color(black)) ///  
graphregion(color(white)) ylabel(, grid glcolor(gs14))

My graph currently looks like the below

[Bruce Weaver]

Does this give you what you want?

format firstr_birth secondr_birth %tdNN/YY

By the way, I found that by typing help format, and then clicking on [D] datetime display formats.

HTH.

[Nick Cox]

Sorry, but Bruce's advice is on this occasion not obviously going to solve the problem. The variables

 secondr_birth firstr_birth

are implied to be date-times in milliseconds from the start of 1 January 1960. If that is not so, why do they have a date display format %tc assigned?

All we can see is a value 2.15 billion but even that is only a date-time within January 1960.

So you need to convert them to monthly dates to get anywhere. You can't do that by assigning them a different display format.

Let's make this concrete. As I write it is 17:39 in my time zone. That is getting for 2 trilllion milliseconds since the start of 1 January 1960. And I do mean trillion.

. di %13.0f clock("2019 Jan 11 17:39", "YMD hm")
1862847540000

If you now assign that variable a daily date display format, you are telling Stata "I really have daily dates in that variable".

So, it can try to interpret them as daily dates 2 trillion days after the start of 1960, modulo a hundred or two billion.

I am not clear that your data are in good shape, but I doubt that is what you need.

Please start again, read and act on FAQ Advice #12

https://www.statalist.org/forums/help#stata

-- and give us a data example using dataex (and swing by #18 on your way back).

On the information you've given you need to push your date-times through mofd(dofc()) -- but I would like to see a data example to be sure.