Storing the value of a variable from one observation in a local macro or scalar

[Brent Fulton]

Dear Statalist,

I'm using Stata 16.0 trying to store a variable value from one observation in a local macro (if the variable is a string) or in a scalar (if the variable is numeric).

Please see my example below. I cannot get the code to work because Stata does not allow "if" when defining locals and scalars. I tried also tried to use the list command (e.g., list make if price=4099), but was not sure how to store the output of the list command.

I'd appreciate your advice.

Thanks,
Brent

. *Here's an example
. sysuse auto
(1978 Automobile Data)

. 
. *In the first observation, the make variable is "AMC Concord" and the price variable is 4,099
. list make price if _n==1

     +---------------------+
     | make          price |
     |---------------------|
  1. | AMC Concord   4,099 |
     +---------------------+

. 
. *I would like to store AMC Concord in the local macro x, but this command doesn't work
. local x1 = make if price==4099
if not allowed
r(101);

end of do-file

r(101);

. do "C:\Users\fultonb\AppData\Local\Temp\STD627c_000000.tmp"

. *Also, I would like to store price in a scalar, but this command doesn't work
. scalar x2 = price if make=="AMC Concord"
if not allowed
r(101);

end of do-file

r(101);

[Nick Cox]

local x1 = make[1] 

scalar x2 = make[1]

[Brent Fulton]

Hi Nick,
Thank you for your response, but I'm sorry I wasn't more clear. I need to be able to use the -if- (or some alternative since if doesn't work) when defining my local macro and scalar because I don't know the observation number for my actual data.
For a scalar, I realize I could use the summarize function and store the mean in the scalar x2 using r(mean) (see the code below).
But this approach does not work for a string variable.
I'd appreciate your advice.
Best,
Brent

. sysuse auto
(1978 Automobile Data)

. summarize price if make=="AMC Concord"

    Variable |        Obs        Mean    Std. Dev.       Min        Max
-------------+---------------------------------------------------------
       price |          1        4099           .       4099       4099

. scalar x2 = r(mean)

. di scalar(x2)
4099

[Andrew Musau]

If the value is distinct, you can use -levelsof-

sysuse auto, clear
levelsof make if price==5705, local(wanted) clean
di "`wanted'"

Res.:

. levelsof make if price==5705, local(wanted) clean
Chev. Impala

. 
. di "`wanted'"
Chev. Impala

[Brent Fulton]

Thank you, Andrew, that works.
Best,
Brent