Patrick Royston

English

Research Papers in Economics

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J. Patrick Royston
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The Stata Journal, electronic version (ISSN 1536-8734) is a publication of Stata Press, and Stata is a registered
trademark of StataCorp LP.The Stata Journal (2005)
5, Number 1, pp. 43–45
Stata at 20: a personal view
Patrick Royston
I bought my ﬁrst copy of Stata in May 1989, and it was version 2.05. I still use
Stata most days, but now it is version 8.2. Why has it survived and prospered so long
in my statistical armory?
I still have my 1989 shipment of Biturbo Stata version 2.05 and Stage 1.0 Graphics
Editor, on ﬁve 3.5-inch, 720 Kb ﬂoppies. On opening at random my copy of the ver-
sion 2.05 reference manual (copyright March 1989 c  Computing Resource Center, Los
Angeles, California), the page fell open at page 539, a summary of something called
Stat.Kit. I recalled then the excitement of the arrival of “kits”; they were the fore-
runners of the now familiar and quintessential ado-ﬁles. In those days, there were 4
such kits (Stat.Kit, Graph.Kit, Data.Kit, Survive.Kit), and they provided a variety
of programs in each relevant area. You typed, for example, run Stat.Kit, and the
associated 17 programs were loaded into memory. After that you used them exactly as
one now does an ado-ﬁle.
On reﬂection, Stata has a few key features that I value above all. First, I will
illustrate one of these features in a little detail, and later I will brieﬂy mention the others.
This feature is backwards compatibility, which in Stata lingo is known as “version
control”. As a simple experiment designed to test version control, I wrote and ran in
Stata 8.2 the following do-ﬁle:
/*
Experiment to show version control.
Patrick Royston.
*/
* Set up version
version 2.05
set logtype text
log using stata.log, replace
* clear out all ado-file support
quietly forvalues j = 1/7 {
adopath -1
}
* Load Stat.Kit
run stat.kit
* Load old auto data
use auto
* Create mpg + uniform() * 5
gen mpg2 = mpg + uniform() * 5
* Perform equal-variance t-test
ttest mpg = mpg2
log close
What I am doing here is to set Stata 8.2 to version 2.05, remove all ado-ﬁle support,
load Stat.Kit and the classic auto.dta dataset, generate a new variable mpg2 from mpg
c  2005 StataCorp LP gn002444 Stata at 20: A personal view
with on average about 2.5 mpg greater values, and run an unpaired t-test comparing
mpg with mpg2. Here is the output as stored in stata.log:
--------------------------------------------------------------------------------
log: e:\tsj\stata20\stata.log
log type: text
opened on: 28 Dec 2004, 10:03:35
. * clear out all ado-file support
. quietly forvalues j=1/7 {
. * Load Stat.Kit
. run stat.kit
Loading Stat.Kit Release 2.05 Copyright (c) 1986-1989 by ==C=R=C==
All rights reserved.
The following new commands are now available:
blogit genstd kwallis signrank ttest
bprobit glogit means signtest
dbeta gprobit ranksum spearman
genrank ksmirnov regdw teststd
See help Stat.Kit.
. * Load old auto data
. use auto
(1978 Automobile Data)
. * Create mpg + uniform() * 5
. gen mpg2 = mpg + uniform() * 5
. * Perform equal-variance t-test
. ttest mpg = mpg2
Variable | Obs Mean Std. Dev. Min Max
-------------+--------------------------------------------------------
mpg | 74 21.2973 5.785503 12 41
mpg2 | 74 23.68922 5.945047 14.43152 44.18587
Test: means of mpg and mpg2 are equal (assuming equal variances)
Difference = -2.3919258
t-statistic = -2.48 with 146 d.f.
Prob > |t| = 0.0143
. log close
log: e:\tsj\stata20\stata.log
log type: text
closed on: 28 Dec 2004, 10:03:35
--------------------------------------------------------------------------------
Lo and behold, Stata 8.2 runs correctly under version 2.05 control using 2.05 program
code and data. This to my mind is impressive. How many other statistical packages
would stand up to such a severe test? For me, version control is an apparently unglam-
orous property of Stata that shows StataCorp’s strong commitment to the practical
needs of its users, and is one reason why Stata still has a rosy future. I dread to think
how many lines of C program code sit behind the scenes supporting the innocent-looking
version # command. Surely this is virtuoso computer programming of a high order?
Other essential features of Stata I particularly value are its graphics, its simple but
elegant command syntax (which in essence has not changed since version 2.05), its
seamless programmability via ado-ﬁles, and last, but by no means least, its excellent
documentation. I do recall that having fast, high-resolution graphics was in 1989 anP. Royston 45
important selling point and a key determinant of why I bought Stata. The fact that
formulas are given in the manual even for quite complex mathematical calculations
such as the partial likelihood in a Cox regression model has been immensely useful, and
StataCorp even now continues to pay attention to improving this aspect of the product.
I could add other far-sighted innovations that were even rather shocking at the time of
their introduction, such as increasing levels of integration with the Internet for updating
Stata and for installing add-on packages. Certainly the list-server Statalist has played a
useful role in the development of user awareness, although I myself don’t ﬁnd much time
to access it nowadays. One must also mention the Stata Journal and its predecessor,
the Stata Technical Bulletin. No serious package can be without such a publication.
Is Stata now perfect? Of course not. Areas in which I would like to see improvements
include documentation of graphics and GUI dialog programming, greater searchability
and ﬂexibility of the help system (I have lost count of the number of times I have trawled
through the help system in search of some obscure graphics option), acceleration of
drawing a graph, and a facility to make it easier to write help ﬁles in Stata’s markup
language, SMCL. A graphics editor would be nice too; my 1989 shipment included Stage
1.0, the ﬁrst and only edition of the Stata graphics editor, a ﬁne program that has not
yet been replaced.
Above all, though, StataCorp’s encouragement of users to get involved and Stata-
Corp’s habit of valuing and responding to their subsequent eﬀorts have been some of the
most delightful and productive aspects of Stata. If that interaction is ever lost, Stata
will probably die.
About the Author
Patrick Royston is a medical statistician of 25 years of experience, with a strong interest in
biostatistical methodology and in statistical computing and algorithms. At present, he works
in clinical trials and related research issues in cancer. Currently he is focusing on problems
of model building and validation with survival data, including prognostic factors studies, on
parametric modeling of survival data, and on novel trial designs.

Stata at 20: a personal view

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Stata at 20: a personal view

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