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Stata FAQ
Can I do by and sort in one command?

When you want to use by var: command you need to first sort var beforw uaing the by, however, it is possible to the by and the sort into a single command.

Let's illustrate use of the process using the high school and beyond dataset.
use http://www.ats.ucla.edu/stat/stata/notes/hsb2, clear
(highschool and beyond (200 cases))
If we wanted summary statistics for each ses group, we would need to use sort and then by as illustrated below.
sort ses
by ses: summarize read write

-------------------------------------------------------------------------------------------------------------
-> ses = low

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
        read |        47     48.2766    9.342987         28         68
       write |        47    50.61702    9.490391         31         65

-------------------------------------------------------------------------------------------------------------
-> ses = middle

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
        read |        95    51.57895    9.425609         31         73
       write |        95    51.92632    9.106044         31         67

-------------------------------------------------------------------------------------------------------------
-> ses = high

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
        read |        58        56.5    10.85834         34         76
       write |        58    55.91379    9.442874         33         67
Here is one way to accomplish this with in a single step. 
 by ses, sort: summarize read write

-------------------------------------------------------------------------------------------------------------
-> ses = low

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
        read |        47     48.2766    9.342987         28         68
       write |        47    50.61702    9.490391         31         65

-------------------------------------------------------------------------------------------------------------
-> ses = middle

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
        read |        95    51.57895    9.425609         31         73
       write |        95    51.92632    9.106044         31         67

-------------------------------------------------------------------------------------------------------------
-> ses = high

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
        read |        58        56.5    10.85834         34         76
       write |        58    55.91379    9.442874         33         67
Alternatively, it is possible to combine by and sort into a single bysort command. The bysort command looks like this: 
bysort ses: summarize read write

-------------------------------------------------------------------------------------------------------------
-> ses = low

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
        read |        47     48.2766    9.342987         28         68
       write |        47    50.61702    9.490391         31         65

-------------------------------------------------------------------------------------------------------------
-> ses = middle

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
        read |        95    51.57895    9.425609         31         73
       write |        95    51.92632    9.106044         31         67

-------------------------------------------------------------------------------------------------------------
-> ses = high

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
        read |        58        56.5    10.85834         34         76
       write |        58    55.91379    9.442874         33         67

For More Information

For more information, see the help or reference manual about the sort command and by.

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