[U] User's Guide

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340 [ U ] 25 Working with categorical data and factor variablesfor variables that divide the data into more than two groups, and let’s use the term indicator variablefor categorical variables that divide the data into exactly two groups.Stata can convert continuous variables to categorical and indicator variables and categorical variablesto indicator variables.25.1.1 Converting continuous variables to indicator variablesStata treats logical expressions as taking on the values true or false, which it identifies with thenumbers 1 and 0; see [U] 13 Functions and expressions. For instance, if you have a continuousvariable measuring a person’s age and you wish to create an indicator variable denoting persons aged21 and over, you could type. generate age21p = age>=21The variable age21p takes on the value 1 for persons aged 21 and over and 0 for persons under 21.Because age21p can take on only 0 or 1, it would be more economical to store the variable as abyte. Thus it would be better to type. generate byte age21p = age>=21This solution has a problem. The value of age21 is set to 1 for all persons whose age is missingbecause Stata defines missing to be larger than all other numbers. In our data, we might have nosuch missing ages, but it still would be safer to type. generate byte age21p = age>=21 if age=21that may have occurred to you:. generate age21p = 1 if age>=21That does not produce the desired result. This statement makes age21p 1 (true) for all persons aged21 and above but makes age21p missing for everyone else.If you followed this second approach, you would have to combine it with. replace age21p = 0 if age
[ U ] 25.1 Continuous, categorical, and indicator variables 341. use http://www.stata-press.com/data/r11/agexmpl. generate byte agecat=21 if age21 & age38 & age64 & age
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A Stata Press PublicationStataCorp
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iTable of contentsStata basics1 Rea
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iii8.2 The return message for obtai
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v14 Matrix expressions . . . . . .
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vii18.11.6 Writing online help . .
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ix25.2.15 Treatment of empty cells
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Stata basics1 Read this—it will h
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4 [ U ] 1 Read this—it will helpA
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36 [ U ] 2 A brief description of S
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38 [ U ] 2 A brief description of S
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40 [ U ] 3 Resources for learning a
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[ U ] 4.3 help: Stata’s help syst
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52 [ U ] 4 Stata’s help and searc
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58 [ U ] 5 Flavors of Stata5.2 Stat
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60 [ U ] 5 Flavors of StataThe diff
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62 [ U ] 6 Setting the size of memo
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8 Error messages and return codesCo
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[ U ] 8.2 The return message for ob
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76 [ U ] 9 The Break key9.2 Side ef
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78 [ U ] 10 Keyboard usesave is the
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80 [ U ] 10 Keyboard use10.4 Editin
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82 [ U ] 10 Keyboard useAnother met
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11 Language syntaxContents11.1 Over
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[ U ] 11.1 Overview 8711.1.2 by var
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[ U ] 11.1 Overview 89. summarize m
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[ U ] 11.1 Overview 91Example 7Nega
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11.1.7 options[ U ] 11.1 Overview 9
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[ U ] 11.1 Overview 9511.1.8 numlis
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[ U ] 11.2 Abbreviation rules 97by
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[ U ] 11.3 Naming conventions 99The
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[ U ] 11.4 varlists 101You may use
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[ U ] 11.4 varlists 103Consider a v
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[ U ] 11.4 varlists 105Here are som
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[ U ] 11.4 varlists 107You can sele
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[ U ] 11.4 varlists 109. use http:/
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[ U ] 11.5 by varlist: construct 11
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[ U ] 11.5 by varlist: construct 11
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[ U ] 11.6 File-naming conventions
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12 DataContents12.1 Data and datase
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[ U ] 12.2 Numbers 119. display 2/0
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[ U ] 12.2 Numbers 121Technical not
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[ U ] 12.4 Strings 12312.4 StringsA
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[ U ] 12.5 Formats: Controlling how
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[ U ] 12.6 Dataset, variable, and v
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[ U ] 12.8 Characteristics 139You c
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[ U ] 12.10 References 141The Varia
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144 [ U ] 13 Functions and expressi
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162 [ U ] 14 Matrix expressionsHere
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164 [ U ] 14 Matrix expressionsWe c
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166 [ U ] 14 Matrix expressions. ma
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168 [ U ] 14 Matrix expressionsRega
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170 [ U ] 14 Matrix expressionsEith
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172 [ U ] 14 Matrix expressionsThe
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174 [ U ] 14 Matrix expressions7. W
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176 [ U ] 15 Saving and printing ou
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182 [ U ] 16 Do-filesYou then enter
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184 [ U ] 16 Do-files* a sample ana
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186 [ U ] 16 Do-files16.1.4 Error h
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188 [ U ] 16 Do-filesMany users inc
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190 [ U ] 16 Do-files5. If Stata is
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192 [ U ] 16 Do-filesyou could writ
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17 Ado-filesContents17.1 Descriptio
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[ U ] 17.5 Where does Stata look fo
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17.6 How do I install an addition?A
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18 Programming StataContents18.1 De
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[ U ] 18.2 Relationship between a p
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[ U ] 18.3 Macros 205That problem i
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[ U ] 18.3 Macros 207For the right
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[ U ] 18.3 Macros 209To a programme
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[ U ] 18.3 Macros 211Because Stata
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[ U ] 18.3 Macros 213Above we have
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[ U ] 18.3 Macros 21518.3.10 Advanc
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[ U ] 18.4 Program arguments 217You
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[ U ] 18.4 Program arguments 219Let
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[ U ] 18.4 Program arguments 221Equ
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[ U ] 18.4 Program arguments 223pro
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[ U ] 18.4 Program arguments 22518.
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[ U ] 18.7 Temporary objects 22718.
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[ U ] 18.8 Accessing results calcul
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[ U ] 18.9 Accessing results calcul
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[ U ] 18.10 Saving results 2333. Co
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[ U ] 18.10 Saving results 2355. Yo
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[ U ] 18.11 Ado-files 237e(sample)
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[ U ] 18.11 Ado-files 239If you wri
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[ U ] 18.11 Ado-files 241duck is co
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[ U ] 18.11 Ado-files 243begin fvar
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[ U ] 18.11 Ado-files 245begin fvar
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Technical note[ U ] 18.11 Ado-files
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[ U ] 18.11 Ado-files 249{phang}{op
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[ U ] 18.11 Ado-files 2515. Include
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[ U ] 18.13 References 253Technical
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256 [ U ] 19 Immediate commands19.1
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258 [ U ] 19 Immediate commands19.1
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260 [ U ] 20 Estimation and postest
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Page 328 and 329: 316 [ U ] 21 Inputting data21.2 Det
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Page 337 and 338: 22 Combining datasetsYou have two d
Page 339 and 340: 23 Working with stringsContents23.1
Page 341 and 342: [ U ] 23.4 Complex strings 329The p
Page 343 and 344: 24 Working with dates and timesCont
Page 345 and 346: [ U ] 24.2 Inputting dates and time
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Page 349 and 350: [ U ] 24.6 Converting between date
Page 351: 25 Working with categorical data an
Page 355 and 356: [ U ] 25.2 Estimation with factor v
Page 369 and 370: 26 Overview of Stata estimation com
Page 371 and 372: [ U ] 26.3 ANOVA, ANCOVA, MANOVA, a
Page 373 and 374: [ U ] 26.5 Binary-outcome qualitati
Page 375 and 376: [ U ] 26.9 Exact estimators 363In t
Page 377 and 378: [ U ] 26.14 Models with time-series
Page 379 and 380: [ U ] 26.15 Panel-data models 367xt
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Page 383 and 384: [ U ] 26.21 Multivariate and cluste
Page 385: [ U ] 26.25 Reference 373should try
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Page 390 and 391: 378 [ U ] 28 Using the Internet to
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390 Subject and author indexcoeffic
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392 Subject and author indexIif exp
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394 Subject and author indexPiantad
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396 Subject and author indexUnix,ke
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