Introduction to Stata 8

Intro'()tion to +tata -
+.en' 0((1
Department o5 Epi'emio1og8 an' +o)ia1 9e'i)ine: Uni.er(

Content<
DE In

Pre5a)e
+tata i< a ing< a1moere t>e 'o)(mentation
o5 I>at 8o( 'i' ] in)1('ing t>e ome page< IIIEe grap>i)< (inge

Potation in t>i< ?ooY1et
+tata )omman'< are oIn 1iYe t>ie o(tp(t eQamp1e< 8o( Ii11 o5ten e )omman'< pre)e'e' ?8 a perio'W
. tabulate agegr sex , chi2
X>i< i< >oI )omman'< 1ooY in o(tp(t: ?(t 8o( o(1' not t8pe t>e perio' 8o(ren
entering a )omman'E
[ptiona1 part< o5 )omman'< are oIn in 1ig>t t8pe5a)e an' en)1oat )ae8 are oIn in
t>e (e eQamp1e< I>en opening dusec or ro(g>o(t t>e teQt I (

DE IntZ e 'eate.er 8o(r perU: 'ataU an' 'oU5i1e< in 5o1'er< organia< at 1ea program 5i1e<
U \o( )an

X>e pro5i1eE'o 5i1e gG+Hh AK
I5 8o( p(t a profile.do 5i1e in t>e c:\ado\personal 5o1'er @ t>e )omman'< Ii11 ?e
eQe)(te' a(tomati)a118 ea)> time 8o( open +tataE Hrite 8o(r profile.do (e replace option
o.erIrite< o1' o(tp(tE X>e 5o1'er c:\tmp m(e append option Yeep< t>e
)omman' 1og 5rom pre.io(< e Reoig>1ig>t error mei< p1a)e i<

@E Hin'oI< in +tata gG+Hh @
I +(ggee main Iin'oI< a< oIn ?e1oIE [n)e 8o( ma'e 8o(r )>oi)e

OieIer Iin'oI gG+Hh G
X>e main (i< Iin'oI i< .ieIing >e1p 5i1e< dat: oI to (e edit )omman' to maYe )orre)tion< 'ire)t18
in t>e 'ata Iin'oIE Vor reae DoU?(ttonE I pre5er PoteXa? Sig>t to t>e 'oU5i1e e'itorZ

GE +(ggee re)ommen'ation< in t>i< at i< re)ommen'e' in t>e gG+Hh
man(a1Z I tr8 to eQp1ain I>8: I>en m8 re)ommen'ation< 'i55erE
GEDE Ie )omman'< in a 'oU5i1e ?e5ore eQe)(tionE
X>e 'ia1og< dmen( e e 'oU5i1eE
! X>e 'oU5i1e e )(rrent 5i1e
?8 )1i)Ying t>e 'oU?(tton dn(m?er tIo 5rom t>e rig>tcE X>e 'iat t>e name o5 8o(r 'oU5i1e i< not re51e)te' in t>e o(tp(tE I re)ommen' ie 'oU5i1e: 5or rea

GE@E _an'1ing o(tp(t
+tataf< o(tp(t 5a)i1itie< are 1ean optima1E In t>i< oI 8o( )an (e t>ir'U
part8 program PoteXa? to >an'1e o(tp(t 5or e'iting an' printingE
X>e Ree Re too in51eQi?1eE X>e +9CSU
5ormatte' o(tp(t i< a miQe' ?1ee gG+Hh man(a1 (e nt )omman' gi.e< 8o( rapi' a))ee 5i1e: I>i)> i< not o.erIritten neQt time +tata i< opene'E
\o( ma8 (e tri)Y )orre)t18: Hin'oI< m(

BE Getting >e1p gG+Hh B: DM: @AZ gUh @: -
BEDE X>e man(a1<
+ee re)ommen'ation< in Appen'iQ DE
BE@E [n1ine >e1p gG+Hh BZ gUh -: G@
[n1ine >e1p i< ?ee OieIer Iin'oI de +tata )omman'
1ineE keep 8o(r +tata (p'ate' ] t>en 8o(r on1ine >e1p i< (p'ate' tooE
help an' whelp
I5 8o( YnoI t>e )omman' name deEgE tabulatec e >e1p 5i1e dta?(1ateE>1pc ?8W
help tabulate 5rom t>e OieIer )omman' 1ineW or
whelp tabulate 5rom +tatal< )omman' 1ine Iin'oI
X>e >e1p 5i1e i< 'ie net 5or in5ormation on goo'ne

JE +tata 5i1e t8pe< an' name< gUh DBEN
E'ta 5i1ei)< man(a1c
+tata grap>< )an ?e

NE Oaria?1e<
A +tata 'ata ere i< one Iit> 5i.e o?e n(m?er<
0-9 an' _ d(n'er

P(meri) 5ormat< gUh DJEJED
X>e 'e5a(1t i< Genera1 5ormat: prein' t>e mi

KE Comman'

In )omman'< t>at >a.e a 'epen'ent .aria?1e: it i< t>e 5ire varlistW
oneway bmi sex bmi i< t>e 'epen'ent .aria?1e
regression bmi sex age bmi i< t>e 'epen'ent .aria?1e
scatter weight height t i< 8UaQi<
tabulate expos case X>e 5ir

y an' bysort pre5iQ gUh DBEJ
9aYe< a )omman' 'i *
! teQt i< ?ooY1etc
X>e p(rpoan
-A )>ara)tere pro?1em i<

-E Getting 'ata into +tata gUh @BZ gG+Hh K
[n eQ)>ange o5 'ata Iit> ot>er programer in5ormation in appen'iQ @E
Enter 'ata a< )omman'< or in a 'oU5i1e gRh input
Very small data sets. De5ine t>e .aria?1e< Iit> t>e input )omman' an' enter t>e .a1(e endE It )an ?e 'one intera)ti.e18 5rom t>e )omman' 1ine or in a 'oU5i1eE +ee
more eQamp1e< in eQamp1e

Rea'ing A+CII 'ata gUh @B
Rea'ing ta?U or )ommaUara)ter: >ere 'ie 5o11oIing eQamp1e<
t>e .a1(e o5 type in o?o(t .aria?1e name< in roI D t>e )omman' ie )omman' i<
infile id type sold price using c:\dokumenter\p1\a.txt
infile 'oe< not ae
5o11oIing 'ata are t>e e 'ata a?o.eW
1 2 47 51.23 2 . 793 199.70
Rea'ing 5iQe' 5ormat 'ata gRh infixZ gRh infile d5iQe' 5ormatc
In 5iQe' 5ormat 'ata t>e in5ormation on ea)> .aria?1e i< 'etermine' ?8 t>e poe 1ineE
X>e ?1anY type in o?

ME Do)(mentation )omman'< gG+Hh -
+tata 'oe< not nee' 'o)(mentation )omman'e
o(tp(t ?e)ome< more 1egi?1e: an' t>e rien interpreting t>e o(tp(t i< re'()e'E
Data e )reation 'ate: to enat 8o( ana18e moi< i< a tIoUe 1a?e1 d'o(?1e ^(ote< aro(n' teQt Iit> em?e''e' ?1anYe .aria?1e sexW
label values sex sexlbl
Ue e .a1(e 1a?e1: to a.oi' mie 1a?e1i< >appen< a(tomati)a118 Iit>W
numlabel _all , add
D-

+ee 1a?e1 'e5inition<
+ee t>e .a1(e 1a?e1 'e5inition< ?8W
label list or
labelbook
+ee t>e .aria?1e 1a?e1 'e5inition< ?8W
describe
+ee a 5(11 )o'e?ooY ?8W
codebook
Pote< gRh notes
\o( ma8 a'' note< to 8o(r 'ata

DAE 9o'i58ing 'ata
Donft mie tit1e o5 t>i< e 1ae 'oU5i1e o(1' ?e f)1eanf: ieE not in)1('e )omman'< irre1e.ant to t>e mo'i5i)ation

generate; replace gRh generate
Generate a neI .aria?1e ?8W
generate bmi=weight/(height^2)
I5 t>e target .aria?1e dbmic a1rea'8 eQie 'ata

ecode gRh recode
C>ange< a .aria?1ef< .a1(ee neI .aria?1e ma8 ?e in)1('e' at on)eW
recode age (55/max=4 "55+")(35/55=3 "35-54")(15/35=2 "15-34") ///
(min/15=1 "-14") , generate(agegr)
Very importantW X>e generate option )reate< a neI .aria?1e Iit> t>e re)o'e'
in5ormationZ Iit>o(t generate t>e origina1 in5ormation in age Ii11 ?e 'ee CPR n(m?er<
Iere

DAE@E +e1e)tion<
+e1e)ting o?e 5ir

DAEBE +orting 'ata
sort gRh sort: gRh gsort
Xo

DAENE Com?ining 5i1e< gUh @J
Appen'ing 5i1e< gRh append
Xo )om?ine t>e in5ormation 5rom tIo 5i1e< Iit> t>e e e eQamp1e a?o.ec: an'
t>e mat)>ing Ye8 m(a.e t>e 'ata ing Ye8 t>e
.aria?1e name< o(1' ?e 'i55erentE `e1oI A an' ` e .aria?1e e inp(t
5i1ee .aria?1e _merge I>i)> taYe< t>e .a1(e D i5 on18 'ata ere Iere tIo o?e ree in5ormation 5rom filb ae '(p1i)ate lbnr B Ia< an errorv Xo )>e)Y 5or '(p1i)ate i'f< ?e5ore merging:

DAEKE Reaping 'ata
collapse gRh collapse
\o( Iant to )reate an aggregate' 'ata t>e )>ara)teri in'i.i'(a1: ?(t
o5 gro(p< o5 in'i.i'(a1ara)teriFe p>8

DDE De eQamp1e< o5 o(tp(tE
summarize gRh summarize
summarize gi.e< an o.er.ieI o5 .aria?1ee 9in an'
9aQ )o1(mne 'ie ni)e mo'i5i)ation summvl: a1e)Y t>e reer t>an .a1(e 1a?e1<
are 'i

. tab1 rating type dta?1e 5or type not oInc
-> tabulation of rating
quality |
rating | Freq. Percent Cum.
--------------+-----------------------------------
1. poor | 6 17.14 17.14
2. acceptable | 9 25.71 42.86
3. good | 16 45.71 88.57
4. excellent | 4 11.43 100.00
--------------+-----------------------------------
Total | 35 100.00
tab2 gRh tabulate
tab2 Iit> tIo .aria?1e< gi.e a tIoUIa8 ta?1e d)roe )omman'W
tab2 rating type nation
gi.e< t>ree tIoUIa8 ta?1e o5 t>e )om?ination< o5 t>e .aria?1ee re
DD .aria?1e< 8o( get JJ tIoUIa8 ta?1ee 1o)a1 ma)ro Q i< a e )omman'< generate DA )omman'

tabi gRh tabulate
tabi i< an fimme'iatef )omman' dort

DDE@E Contin(o(< .aria?1e<
oneway gRh oneway
)ompare< mean< ?etIeen tIo or more gro(p< dana18 F
------------------------------------------------------------------------
Between groups 780.660217 3 260.220072 0.98 0.4162
Within groups 8257.34954 31 266.366114
------------------------------------------------------------------------
Total 9038.00975 34 265.823816
Bartlett's test for equal variances: chi2(3) = 2.3311 Prob>chi2 = 0.507
X>e ta?1e: ?(t not t>e tean'1e< a 1ot o5 )omp1eQ e 'ie

ttest gRh ttest
XUte

D@E Regre

D@E@E Sogie xi: pre5iQ app1ie< a< 'e

DGE +(r.i.a1 ana18e 'ata e 'ata in memor8 to ?e e timeUo5UeQit .aria?1eW
. // c:\dokumenter\proj1\gen.st.cancer1.do
. use c:\dokumenter\proj1\cancer1.dta , clear
.
stset risktime , failure(died==1) id(lbnr)
id: lbnr
failure event: died == 1
obs. time interval: (risktime[_n-1], risktime]
exit on or before: failure
-------------------------------------------------------------------------
48 total obs.
0 exclusions
-------------------------------------------------------------------------
48 obs. remaining, representing
48 subjects
31 failures in single failure-per-subject data
62 total analysis time at risk, at risk from t = 0
earliest observed entry t = 0
last observed exit t = 3.25
GB

. summarize
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
lbnr | 48 24.5 14 1 48
.... |
risktime | 48 1.291667 .8546908 .0833333 3.25
died | 48 .6458333 .4833211 0 1
_st | 48 1 0 1 1
_d | 48 .6458333 .4833211 0 1
_t | 48 1.291667 .8546908 .0833333 3.25
_t0 | 48 0 0 0 0
. save c:\dokumenter\proj1\st.cancer1.dta
Vo(r neI .aria?1e< Iere )reate': an' t>e stfe' 'ata erIiW g+Xh sts graph
sts graph , by(drug)
Xo o?tain a )(m(1ati.e in)i'en)e dD]+c grap> 'ie inter.a1 AUAE@J at t>e 8UaQi

In)1('ing age in t>e ana18

poisson gRh poisson
X>e stsplit.cancer2.dta 'ata

DBE Grap><
DBEDE Intro'()tion
X>e p(rpoi< e1p 8o( (n'eroi)ean [OK]Z t>i< gi.e< t>e opport(nit8 to mo'i58 8o(r )>oi)e< a5ter >a.ing
1ooYe' at t>e rei< Ia< t>e eae p(rpoe 5irere i< 'i55erent 5rom t>e man(a1 i< i

DBE@E X>e anatom8 o5 grap><
Vig(re D oI< t>e moE X>e graph area i< t>e entire 5ig(re:
in)1('ing e.er8t>ing: I>i1e t>e plot area i< t>e )entra1 part: 'e5ine' ?8 t>e aQee o.era11 )omman'< ii< i< t>e

H>en 1etting t>e 'ia1og generate a e grap> t8peZ scatter 'e5ine< a p1ot in t>e grap>E \o( )o(1' enter t>e
e )omman' Iin'oI: ?(t +tata a1i< ort .ere .aria?1e 1ii)> )ome< 1a )omman'< ma8 >a.e optioner +tata )omman'< a )omma pre)e'e< t>e
optione twoway grap> )omman'W
twoway (scatter mpg weight) , title("74 car makes")
P1ot a.e optione p1ot ara)tercW
title"("74 car makes")
X>e error meee entire grap> e ae p1ot area dt>e 8eQ aQi< ratioc ?8 t>e
aspect() optionE Xo o?tain a

Xi)Ye QUaQi maaor inter.a1 in tIoE X>e 8UaQi< >a< a 1og e aQee 'e5a(1t i< >oriFonta1 gri'1ine< an'
no .erti)a1 gri'1inear'18 a goo' i'ea in
t>i< )aer t>an perio'e +tata )omman'W
set dp comma
P1otregion margin
`8 'e5a(1t tIoIa8 grap>< in)1('e a margin ?etIeen t>e eQtreme p1ot .a1(e< an' t>e aQe e1ement<
X>e p1a)ement o5 grap> e1emente 1egen': i< 'e5ine' ?8 1o)ation re1ati.e to t>e p1ot
area dring poe eme app1ie' d

A teQt ?1o)Y i< p1a)e' in t>e p1ot area ?8 gi.ing it< 8 an' Q )oor'inatee
'e5a(1tc mean< t>at t>e )oor'inate< app18 to t>e )enter o5 t>e teQt ?1o)YZ place(se) t>at
t>e8 app18 to t>e ?1o)Yf< ea +8m?o1 +iFe
Segen' et)E color()
5i11 fcolor()
o(t1ine lcolor() lpattern() lwidth()
`ar

X>e 'e5a(1t )onne)tUe )o1o(r o5 t>e bar fill i< 'e5ine' ?8 t>e bfcolor() optionW
... , bar(1, bfcolor(gs9)) bar(2, bfcolor(gs14))
DBEKE EQamp1e<
[n t>e 5o11oIing page< 8o( 5in' i11(at generate' t>e grap>e appearan)e i< 'i55erent 5rom t>e man(a1f< grap>at ma'e it: in)1('ing t>e 'ata 5or t>e grap> or a use
)omman'E I e i11(e grap> e xsize() an' ysize() optionioIe.er: 1ea'< to too ?oQ an' grap> pieE
histogram
N of children
80
60
40
20
0
1000 1500 2000 2500 3000 3500 4000 4500 5000
Birthweight, grams
A >i

c:\dokumenter\...\gph.birthweight.do
u se "C:\dokumenter\...\newborns.dta" , clear
set
scheme lean2
histogram bweight ///
, ///
frequency ///
normal ///
start(750) width(250) ///
xlabel(1000(500)5000) ///
xmticks(##2) ///
xtitle("Birthweight, grams") ///
ytitle("N of children") ///
plotregion(margin(b=0)) ///
xsize(4) ysize(2.3) scale(1.4)
graph bar
Prevalence (per cent)
10
8
6
4
2
0
16-24 25-44 45-66 67-79 80+
Age
/ / c:\dokumenter\...\gph.diabetes prevalence.do
clear
input str5 age m f
16-24 .9 .2
25-44 .8 .8
45-66 3.8 2.9
67-79 8.2 5.4
80+ 9.1 7.2
end
set
scheme lean2
Males
Females
graph bar m f ///
, ///
over(age) ///
b1title("Age") ///
ytitle("Prevalence (per cent)") ///
legend( label(1 "Males") label(2 "Females") ) ///
xsize(4) ysize(2.3) scale(1.4)
Vor

In ?ar grap>< t>e QUaQi< i< )ategori)a1: t>e 8UaQi< )ontin(o(e eQamp1e .aria?1e< m an'
f 'e5ine' t>e >eig>t< o5 t>e ?are )omman' Iere dIit> one o?e ree t>e auto.dta 'ata 8o( )o(1' generate ?ar< 5or t>e n(m?er o5 'omee n(m?er o5 nonUmi Iit> one p1ot >a< no 1egen'Z t>i< one Iit> tIo p1ot< >ae 'e5a(1t 1egen' teQt<
o5ten nee' to ?e rep1a)e' ?8 ort: 'ie xtitle() an'
ytitle() option< Iere not e .aria?1e 1a?e1< a< aQi< tit1ee 'e5a(1t 5ir

twoway line
Per cent surviving
100
80
60
40
20
0
Females
Males
1840-49
1901-05
1999-2000
0 20 40 60 80 100
Age
/ / c:\dokumenter\...\gph.DKsurvival.do
u se c:\dokumenter\...\DKsurvival.dta , clear
sort
age // Data must be sorted by the x-axis variable
list in 1/3, clean // List to show the data structure
age m1840 k1840 m1901 k1901 m1999 k1999
1. 0 100.00 100.00 100.00 100.00 100.00 100.00
2. 1 84.47 86.76 86.93 89.59 99.16 99.37
3. 2 80.58 83.11 85.22 87.89 99.08 99.32
set scheme lean1
twoway ///
(line m1840-k1999 age , clpattern( - l - l – l )) ///
, ///
plotregion(margin(zero)) ///
xtitle("Age") ///
ytitle("Per cent surviving") ///
legend(label(1 "Males") label(2 "Females") order(2 1) ///
ring(0) pos(8)) ///
text(91 72 "1999-2000") ///
text(77 48 "1901-05") ///
text(49 40 "1840-49") ///
xsize(3.3) ysize(2.3) scale(1.4)
A 1ine p1ot i< a .ariation o5 o(t marYer )onne)ting 1inei< grap>
in)1('e< e
clpattern() option 'e5ine< t>e erIie reoI to poe 1egen' Iit>in t>e
p1ot area d

twoway connected; twoway rcap
Mean score
100
80
60
40
20
PF RP BP GH VT SF RE MH
SF-36 subscale
/ / c:\dokumenter\...\gph.SF36a.do
clear
input scale n obs sd norm
1 139 60.81 27.35 70.77
2 139 37.65 42.06 62.01
...
8 139 73.06 21.54 79.99
end
generate se=sd/sqrt(n)
generate ci1=obs+1.96*se
generate
ci2=obs-1.96*se
Observed
Expected
95% CI
label define scale 1 "PF" 2 "RP" 3 "BP" 4 "GH" 5 "VT" 6 "SF" 7 "RE" 8 "MH"
label
values scale scale
set scheme lean1
twoway ///
(connected obs scale , msymbol(O) clpattern(l)) ///
(connected norm scale , msymbol(O) mfcolor(white) clpattern(-)) ///
(rcap ci1 ci2 scale) ///
, ///
ytitle("Mean score") ///
xtitle("SF-36 subscale") ///
xlabel(1(1)8 , valuelabel noticks) ///
xscale(range(0.5 8.5)) ///
legend(label(1 "Observed") label(2 "Expected") label(3 "95% CI")) ///
xsize(4) ysize(2.3) scale(1.4)
X>i< grap> in)1('e< t>ree p1ota.e a )ategori)a1 .aria?1e dPV: RP et)Ec at t>e QUaQii< grap>
e 'io(t )ap

twoway rspike
Cross-sectional study
/ / c:\dokumenter\...\gph.length_bias.do
clear
set obs 20
gen x=_n
gen y1=x
gen y2=y1+2
replace
y2=y1+8 if mod(x,2)==0
set
scheme lean2
twoway (rspike y1 y2 x , horizontal blwidth(*1.5)) ///
, ///
yscale(off) ylabel(, nogrid) ytitle("") ///
xlabel(none) xtitle("Cross-sectional study") ///
xline(14.5) ///
xsize(3.7) ysize(2.3) scale(1.4)
X>e p(rpoi< grap> i< to i11( ?ia

twoway dropline
Patient number
20
15
10
5
1
Deaths
Censorings
0 1 2 3 4 5 6 7
Years after diagnosis
/ / c:\dokumenter\...\gph.obstime.do
use
"c:\dokumenter\...\cohort1.dta" , clear
list patient time died in 1/5 , clean
patient time died
1. 1 0.578 1
2. 2 0.867 1
3. 3 1.235 1
4. 4 1.374 0
5.
5 1.437 1
set
scheme lean2
twoway ///
(dropline time patient if died==1, horizontal msymbol(S)) ///
(dropline time patient if died==0, horizontal ///
msymbol(S) mfcolor(white)) ///
, ///
plotregion(margin(zero)) ///
ytitle("Patient number") ///
yscale(range(0 22)) ///
ylabel(1 5 10 15 20 , nogrid) ///
xtitle("Years after diagnosis") ///
xlabel(0(1)7) ///
legend(label(1 "Deaths") label(2 "Censorings") ring(0)) ///
xsize(3.7) ysize(2.5) scale(1.3)
In a 'rop1ine p1ot a 1ine f'ropeir appearan)e i< )ontro11e' ?8
blpattern(): blcolor() an' blwidth()E
X>e marYer 5or )enite 5i11: not a >o11oI e marYerE
BM

twoway function
-3.00 -1.96 -1.00 0.00 1.00 1.96 3.00
Standard deviations from mean
/ / c:\dokumenter\...\gph.normal.do
set
scheme lean2
twoway ///
(function y=normden(x) , range(-3.5 3.5) ///
droplines(-1.96 -1 0 1 1.96)) ///
, ///
plotregion(margin(zero)) ///
yscale(off) ylabel(, nogrid) ///
xlabel(-3 -1.96 -1 0 1 1.96 3 , format(%4.2f)) ///
xtitle("Standard deviations from mean") ///
xsize(3) ysize(2.3) scale(1.4)
twoway function gi.e< 8o( t>e opport(nit8 to .iemati)a1 5(n)tionE X>e
rea< no re1ation to t>e a)t(a1 'ata in memor8E X>e range() option i< ne)e

graph matrix
40
30
20
10
250
200
150
Price
5,000 10,000 15,000
10 20 30 40
Mileage
(mpg)
graph matrix
// c:\dokumenter\...\gph.matrix.do
sysuse auto , clear
set scheme lean1
Weight
(lbs.)
2,0003,0004,0005,000
graph matrix price mpg weight length ///
, ///
title(graph matrix) ///
mlwidth(*0.7) ///
xsize(5) ysize(4)
150 200 250
Length
(in.)
15,000
10,000
9atriQ e (pper rig>t )e11< are re'(n'ant rotate' image< o5 t>e 1oIer 1e5t )e11em ?8W
graph matrix price mpg weight length , half
JD
5,000
5,000
4,000
3,000
2,000

DBE-E +a.ing: 'ie asis option : it i< 'iat i< not t>e )aer grap>E Remem?er to in)1('e t>e 'ata
or a use )omman' rea'ing t>e 'ata (e grap> )omman' Iit> a grap> 'ia1ogE
[pen a ma8 ?e 'i
ReU'ie )(rrent grap> ?8W
graph display [, scale(1.2) ysize(3) xsize(5) scheme(lean2)]
X>e scale() option i< ( area darg(ment< in in)>eat Ii11 ?e tran

+e1e)t Enhanced Metafile (EMF) or Windows Metafile (WMF)Z I>i)> one IorY< ?ee s2color emeE
X>i< note (e eme< lean1 an' lean2Z t>e8 are mo'i5i)ation< to s1mono an'
s2monoE 9oe 'i55eren)e ?etIeen t>e tIo i< t>at lean1 >a< a 5rame' p1ot area: ?(t no gri'1inei1e
t>e oppoe )a 8o(r oIn pre5eren)e< (er teQt e'itor
to enter t>e option< 8o( Iant in 8o(r oIn per )omman'
termino1og8Z 'o)(mentation i< 5ort>)omingE G
G 0((1 +E Sean maini)e +tata 0o(rna1 @AAGZ GW @MJUGADE
JG

DJE 9ie
memor8 a11o)ate'E X>e memor8 m(ange t>e pat> 5ie1' teQt toW
c:\stata\wstata.exe /m15E
I5 t>e memor8 a11o)ate' i< ine mee p>8i< ma8 re'()e t>e memor8 nee' ?8 -AuE
_an'1ing >(ge 'ata an'1ing >(ge 'ata e 'ata: )ompree neQt part o5 t>e 'ata: )ompree partia1 'ata

DJE@E +tring .aria?1e< gUh DJEBZ gUh @N
X>ro(g>o(t t>i< teQt I >a.e 'emon

Numbers to strings
\o( Iant t>e n(meri) .aria?1e cprnum )on.erte' to a e n(meri) .aria?1e cprnumE _oIe.er: 5or per a
1ea'ing 0 in t>e CPR n(m?er t>e i< )an ?e
reme'ie' ?8W
replace cprstr = subinstr(cprstr," ","0",1)
X>e upper 5(n)tion )on.ert< 1oIer )aa' ?een entere' in)on=10 & ncode4e e infix
)omman' rea' t>e i< Ia8W
replace diab=1 if scode>="E10" & scode

DJEGE Datee n(m?er o5 'a8< : C 5or )ent(r8: Y 5or tIoU'igit 8earcE EQamp1eW
format bdate %dD.N.CY
Rea'ing 'ate .aria?1e< gUh @KE@ED
A 'ate ma8 ?e inp(t a< t>ree .aria?1ee 'ate a< a e date 5(n)tion f(n'eri< e )ent(r8E
Ca1)(1ation< Iit> 'ate< gUh @KE@EB
Xo eQpree 1engt> o5 a time inter.a1 in 8ear< 8o( m(e 'ate in5ormation 5rom t>e

[r 8o( )an eQtra)t Ye8 in5ormation 5rom a CPR n(m?er rea' a< one Z e r(1e< ?e1oIW
generate century = 19
replace century = 20 if pos7 >= 4 & byear = 5 & pos7 = 58
replace byear = 100*century + byear
generate bdate = mdy(bmon,bday,byear)
X>e in5ormation on e 5iret>er t>e e)Y<
t>e .a1i'it8 o5 a CPR n(m?erE Vin' an' 'oIn1oa' it ?8W
findit cprcheck
J-

DJEBE Ran'om

DJEJE Imme'iate )omman'< gUh @@
An fimme'iatef )omman' re^(ire< ta?(1ar or aggregate' inp(tZ 'ata in memor8 are not
a55e)te'E X>e imme'iate )omman'< tabi: cci: csi: iri an' ttesti are mentione' in
e genera1 )omman' ci an' t>e fimme'iate )omman' cii )a1)(1ate )on5i'en)e inter.a1ere oI t>e (

DJENE +amp1e

DJEKE a'oU5i1e< gUh @AU@D: gPh dProgramming man(a1c
An a'oU5i1e i< a programE 9oee on1ine >e1p dwhelp
foreachcE A1in t>e ?ra)e< {} I>i)> m(e opening ^(ote i< ` da))ent gra.ec: an'
t>e en'ing ^(ote t>e

DJE-E EQ)>ange o5 'ata Iit> ot>er program<
`eIareW Xrane)Y )are5(118 egE ?8
)omparing t>e o(tp(t 5rom +P++f DESCRIPTIVES an' +tataf< summarizeE Ee n(m?er o5 .a1i' .a1(e< 5or ea)> .aria?1e an' taYe )are Iit> mi

Vre^(ent18 (

DNE DoU5i1e eQamp1e<
_ere 5o11oI ort eQamp1e< o5 'oU5i1e< 'oing t8pi)a1 t>inger t>an ?8 entering
e e 5ir 'oU5i1e< are part o5 t>e 'o)(mentation an' t>e8 o(1' ?e e8 o(1' >a.e name< te11ing I>at t>e8 'oE 98 prin)ip1e i< t>ii< i< 'i55erent 5rom eQamp1e G I>ere no neI 'ata are
generate': on18 o(tp(tE X>i< 'oU5i1e i< not .ita1 in t>e e 'oU5i1e e'itor 5or )reating
'oU5i1ee 1a

Example 3. Analyse Stata data
// winedes.do Descriptive analysis of the wine data 14.5.2001
use c:\dokumenter\wines\wine.dta
describe
codebook
summarize
tab1 type rating
tabulate type rating , chi2 exact
oneway price rating , tabulate
Pote t>at in eQamp1e D an' @ t>e ange< Iere 'o)(mente' Iit> a
'oU5i1e Iit> a gen. pre5iQE
In eQamp1e G t>e

Appendix 1
P(r)>a epi'emio1ogi)a1 atE
I5 8o( Iant to Irite 8o(r oIn program< da'oU5i1ee Ue +)an'ina.ian (< Uni.er

Appendix 2
EpiData GEA IIIEepi'ataE'Y
EpiData i< an ea t>ree 5i1ee 'e5inition 5i1e I>ere 8o( 'e5ine .aria?1e name< an' entr8 5ie1'e 'ata 5i1e in EpiIn5o N 5ormatE
first.chk i< t>e )>e)Y5i1e 'e5ining .aria?1e 1a?e1ere 8o( 'e5ine .aria?1e namee .aria?1e name: t>e 5o11oIing teQt ?e)ome< t>e .aria?1e 1a?e1E
! ## in'i)ate< a tIoU'igit n(meri) 5ie1':
! ##.# a 5o(rU'igit n(meri) 5ie1' Iit> one 'e)ima1E
! ___ a t>ree )>ara)ter e o?

Oaria?1e name< )an >a.e (p to - )>ara)ter< a-z d?(t not nopc an' 0-9Z t>e8 m(t gi.e it t>e
name sex ] ?(t eEgE a 1a?e1 'e5inition n0y1 dA PoZ D \et 'e5ine a )ommon 1a?e1 5or man8 .aria?1e<
Ue sexlbl 1a?e1 'e5inition 5or sexE [t>er entrie< t>an
D: @: an' not>ing Ii11 ?e reae)te'E
I5 8o( enter D 5or sex: 8o( Ii11 a(mp to t>e .aria?1e
bdateZ e men( ?e1oIE
X>e meaning o5 t>e 9en( 'ia1og ?oQ i< not o?.io(< at 5ire
option<

Appendix 3
PoteXa? Sig>t IIIEnoteta?E)om
`ot> t>e Ree OieIer Iin'oI >a.e 1imitation< in t>e a?i1it8 to >an'1e
o(tp(t: an' 8o( Ii11 ?ene5it 5rom a goo' teQt e'itorE I (t: a.ai1a?1e 5or 5ree
5rom IIIEnoteta?E)omE I 5in' PoteXa? e (e 5o11oIing I ai1e r(nning +tata 8o(
mig>t not e 1atea.e a))ee (p'ate' o(tp(tE [r rig>tU)1i)Y t>e 5i1ef< ta? an'

In'eQ
A
a'oU5i1e< EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE N@
Aggregating 'ataEEEEEEEEEEEEEEEEEE @N
anova EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE GA
append EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE @J
Arit>meti) operator< EEEEEEEEEEEE @A
A+CII 'ata EEEEEEEEEEEEEEEEEEEEEEEEEEE DK
AQi< 1a?e1< dgrap> option< EEEEEEEEEEEEEEEEEEEEEEEEEEEE BB
`art1ettf< te

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