st: -set obs- for -tempfile-

["Lythgoe, Dan" <D.Lythgoe@liverpool.ac.uk>]

Dear Statalisters,

I'm clearly missing something when it comes to -tempfile- and I wonder if you can help. With a data set in memory I want to create a (very small) temporary data set where I can -set obs-, plot a simple graph and then restore the original data. Using a combination of -preserve- and -clear- works fine:

/****START****/
sysuse auto, clear

preserve
clear
set obs 12
gen x = _n
gen y = x^2
line y x 
/****END****/


However I had anticipated that using -tempfile- would do the same but clearly -set obs- is not setting the number of observations for the temporary file but for the original file: 


/****START****/
sysuse auto, clear

tempfile temp
set obs 12
gen x = _n
gen y = x^2
line y x 
/****END****/

Returns the error: 

obs must be between 74 and 2147483646
r(198);


Help would be greatly appreciated.

Many thanks
Dan Lythgoe

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