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st: Re: understanding the difference between gen and egen
Dick is caught by a historical issue here. Prior to Stata 9, you
gen foo = sum(bar)
egen foo = sum(bar)
which was indeed confusing, given that the gen produced a RUNNING sum
and the egen produced a total. Wisely, Stata's developers renamed the
egen function to total().
With respect to the wide array of non-official Stata capabilities
(for the accessibility of which I am somewhat responsible) the Stata
command findit will locate anything that is in the Stata Journal,
Stata Technical Bulletin, or the SSC Archive which I maintain.
Anything you find in the SSC Archive can be described with the ssc
command, and installed likewise. Bill Gould's new official
"adoupdate" command makes it as easy to keep user-installed stuff up
to date as official Stata components. So yes, Stata is more confusing
that a program fully described by a printed manual. Even official
Stata is not fully documented by the version 9 manuals, given
significant additions since 9.0. But "help whatsnew" and "help
forthcoming" will assist with that.
Official Stata is a very dynamic organism, with significant
enhancements during the life of a major version. When the user-
written components made available through the Stata Journal and SSC
Archive are taken into account, you literally have to check daily for
what has been newly developed if you want to be fully au courant. (I
added a number of new routines this week that had been in a backlog
during my absence; "ssc whatsnew" will show them, with links to their
descriptions). Admittedly this can be confusing; but it is also one
of Stata's great virtues and comparative advantages over many
alternative statistical languages.
PS> Confronted with 6 feet + of manuals on a shelf for Some
Alternative Software, some users are comforted?
Kit Baum, Boston College Economics
On Jun 14, 2006, at 2:33 AM, Dick wrote:
I am now a confirmed Stata user and love it for all the reasons
that Phil Schumm outlined the other day and more. But the recent
note from a user regarding sums within id reminds me of how
difficult it is sometimes for new users to get a handle on relatively
simple things. In the current case, if I look up "sum" in the master
index, I am directed to -egen-. If I go to -egen-, somewhat
I don't find -sum- listed in the list of egen functions beginning
on page 101
of the Data Management manual or summary of that list on page 105.
Nor is it available in the drop down list of egen functions
I can do -sum- as a function using -gen- but then I get a running
It struck me that perhaps -help egenmore- would show me the sum
but no luck. A little further digging led me to the documentation
- -sum- function
on page 157 which tells me that I can get a running sum and which
me to an "alternative sum function" in -egen-. What I did
eventually find in
the documentation for -egen- was the -total- function which does
produce a sum. But so does the -sum- function, so one is apparently an
alias for the other.
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