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Re: st: error message after dtobit
At 08:15 PM 5/7/2006, Richard Williams wrote:
You often need to use version control on the estimation command with
user-written post-estimation commands. Stata changes something and
these older post-estimation commands get zapped. Try this:
To follow up on that a bit: If you type -help version- , you find
that if you set version to less than 9,
"14. Commands ologit and oprobit revert to pre-Stata 9 logic in how
e(b) and e(V) are stored. Results were stored in two equations, with
all cut points stored in the second.
"15. Commands tobit and cnreg revert to pre-Stata 9 logic in how
e(b) and e(V) are stored. Results were stored in a single equation
containing both coefficients and the ancillary variance parameter."
So, my guess is that older user-written post-estimation commands
written to work with ologit, oprobit, tobit and cnreg may encounter
problems in Stata 9. There may be others. Unfortunately, the fact
that the user-written command used version control does not help,
because it expects the results stored in e() to be in a certain
format. This seems to affect the user-written commands dtobit,
margeff, and no doubt many others.
The solution is to run the estimation command with version control, e.g.
version 8.2: ologit y x1 x2 x3
Perhaps the authors will eventually update their programs, or if you
are daring you can try to make the modification yourself. Also, some
authors offer different versions of their programs for different
versions of Stata (e.g. the spost programs of Long & Freese; Roger
Newson and Nick Cox are also among the kindly authors who do this).
It is also possible sometimes just to write a little code in your
program that checks for the version of Stata being used and then
adjusts accordingly. When it works, this saves the hassle of having
multiple versions of a program floating around. Or, you might be
able to come up with a more general coding that works regardless of
the version of Stata used.
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
WWW (personal): http://www.nd.edu/~rwilliam
WWW (department): http://www.nd.edu/~soc
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