Introduction to Stata 8 - (GRIPS

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9. Documentation commands [GSW] 8 Stata does not need documentation commands; you need the documentation yourself. The output becomes more legible, and the risk of errors when interpreting the output is reduced. Data set label [U] 15.6.1; [R] label You can give a short description of your data, to be displayed every time you open (use) data. label data "Fertility data Denmark 1997-99. ver 2.5, 19.9.2002" It is wise to include the creation date, to ensure that you analyse the most recent version. Variable labels You can attach an explanatory text to a variable name. label variable q6 "Ever itchy skin rash?" [U] 15.6.2; [R] label Use informative labels, but make them short; they are sometimes abbreviated in output. Value labels [U] 15.6.3; [R] label You can attach an explanatory text to each code for a variable. This is a two-step procedure. First define the label (double quotes around text with embedded blanks): label define sexlbl 1 male 2 female 9 "sex unknown" Next associate the label sexlbl with the variable sex: label values sex sexlbl Use informative labels, but make them short; value labels are often abbreviated to 12 characters in output. Most often you will use the same name for the variable and its label: label define sex 1 male 2 female label values sex sex but the separate definition of the label enables you to reuse it: label define yesno 1 yes 2 no label values q1 yesno label values q2 yesno If you want to correct a label definition or add new labels, use the modify option: label define sexlbl 9 "unknown sex" , modify adds the label for code 9 to the existing label definition. In output Stata unfortunately displays either the codes or the value labels, and you often need to see them both, to avoid mistakes. You may solve this by including the codes in the labels; this happens automatically with: numlabel _all , add 18
See label definitions See the value label definitions by: label list or labelbook See the variable label definitions by: describe See a full codebook by: codebook Notes You may add notes to your data set: note: 19.9.2000. Corrections made after proof-reading and to single variables: note age: 20.9.2000. Ages > 120 and < 0 recoded to missing [R] notes The notes are kept in the data set and can be seen by: notes Notes are cumulative; old notes are not discarded (and that is nice) 19
Page 1 and 2: Introduction to Stata 8 Svend Juul
Page 3 and 4: Preface Stata is a software package
Page 5 and 6: 1. Installing, customizing and upda
Page 7 and 8: 2. Windows in Stata [GSW] 2 The org
Page 9 and 10: 3. Suggested mode of operation The
Page 11 and 12: 4. Getting help [GSW] 4, 19, 20; [U
Page 13 and 14: 6. Variables A Stata data set is re
Page 15 and 16: 7. Command syntax [U] 14.1 Stata is
Page 17 and 18: y and bysort prefix [U] 14.5 Makes
Page 19: Reading ASCII data [U] 24 Reading t
Page 23 and 24: generate; replace Generate a new va
Page 25 and 26: 10.2. Selections Selecting observat
Page 27 and 28: 10.6. Combining files [U] 25 Append
Page 29 and 30: 11. Description and analysis This s
Page 31 and 32: tabi [R] tabulate tabi is an 'immed
Page 33 and 34: ttest [R] ttest T-test for comparis
Page 35 and 36: 12.2. Logistic regression logistic
Page 37 and 38: . summarize Variable | Obs Mean Std
Page 39 and 40: poisson [R] poisson The stsplit.can
Page 41 and 42: 14.2. The anatomy of graphs Figure
Page 43 and 44: You may define maximum and minimum
Page 45 and 46: 14.7. Examples On the following pag
Page 47 and 48: twoway scatter 40 Mileage (mpg) 30
Page 49 and 50: twoway connected; twoway rcap 100 8
Page 51 and 52: twoway dropline 20 Patient number 1
Page 53 and 54: graph matrix 10 20 30 40 graph matr
Page 55 and 56: Submitting graphs to journals etc.
Page 57 and 58: 15.2. String variables [U] 15.4; [U
Page 59 and 60: 15.3. Dates. Danish CPR numbers Dat
Page 61 and 62: 15.4. Random samples, simulations R
Page 63 and 64: 15.6. Sample size and study power s
Page 65 and 66: 15.8. Exchange of data with other p
Page 67 and 68: 16. Do-file examples Here follow sh
Page 69 and 70: Appendix 1 Purchasing Stata and man
Page 71 and 72:
Variable names can have up to 8 cha
Page 73 and 74:
Index A ado-files .................
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