restore and restore,preserve

[wanhaiyou]

Hi,dear all
The routine "preserve" is useful. However, I am not well understand the differences between
preserve
...
restore

and

preserve
...
resotre,preserve

Could anyone give me an example please? Thanks very much


Bests,
wanhaiyou

[Joseph Coveney]

Run the do-file below, and you can see what the difference in behavior is.

version 13.1

clear *
set more off

program define restore_only
    version 13.1
    syntax

    preserve
    // No op
    restore
    drop _all
end

program define restore_preserve
    version 13.1
    syntax

    preserve
    // No op
    restore, preserve
    drop _all
end

sysuse auto

restore_preserve
describe

restore_only
describe

exit

[wanhaiyou]

Thanks very much,Joseph Coveney.
Yes, there exists the difference between two results. The data is empty after running the restore_only, but restore_preserve is not.
However, I am still not well understand. Could you give me more detailed explaination on this issue please?

Bests,
wanhaiyou

[Carlo Lazzaro]

wanhaijou:
-help preserve- will point you to the related entry in Stata 13.1 .pdf manual, where you can find the detailed explanation you need.

Kind regards,
Carlo

[wanhaiyou]

Thanks very much, Carlo Lazzaro.

Bests,
wanhaiyou