INTRODUCTION TO STATA

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INTRODUCTION TO STATA

• Võ Tu?n Khoa
• Tr?n Th? Trung

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Stata basics

• command-driven or menu-driven software
• modeling complex data from longitudinal studies
  or surveys ? deal for analyzing results from
  clinical trials or epidemiological studies
• provides a powerful programming language

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Stata interface in Window
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Stata command
The basic language syntax for STATA commands is
by varlist command varlist exp if exp
in range weight
using filename , options
where the elements between brackets are optional.
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Stata command

• by varlist instructs Stata to repeat the
  command for each combination of values in the
  list of variables varlist.
• command is the name of the command and can be
  abbreviated for example, the command display can
  be abbreviated as dis.
• varlist is the list of variables to which the
  command applies.
• exp is an expression.
• if exp restricts the command to that subset of
  the observations that satis?es the logical
  expression exp.
• in range restricts the command to those
  observations whose indices lie in a particular
  range.
• weight allows weights to be associated with
  observations
• using ?lename speci?es the ?lename to be used.
• options are speci?c to the command and may be
  abbreviated.

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Stata command

• Example 1
• Stata Command
• .bysort black summarize age if year gt 80,
  detail
• Results
• Summarizes age separately for different values of
  black, including only observations for which year
  gt 80, includes extra detail.

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Stata command

• Example 2
• Stata Commands
• .generate agelt30 age
• .replace agelt30 1 if age lt 30
• .replace agelt30 0 if age gt 30 age lt.
• Result variable agelt30 set equal to 1, 0, or
  missing
• Generally exp used with commands generate and
  replace

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Stata command

• Click Help / Stata command
• Type key word (Ex summarize)
• See details

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Do Files and Log Files

• A do file is a text file with STATA code that
  STATA runs line by line, as if the sentences
  where written in the STATA command window.
• A log file is a text file with all the results
  that appear in the STATA results window.
• the user selects when to start and when to stop
  logging to the log file

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Variable name

• Have up to 32 characters but shorter names are
  easy to type
• Stata names are case sensitive (age?Age)
• Should
• short lowercase
• single word
• underscore to separate word
• effort
• fpe
• family_planning_effort
• familyplanningeffort

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Variable type

• Nummeric variable
• String variable
• Missing value
• numberic dot (.)
• string

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Some Basic Commands

• computing basic statistics
• summarize ypc
• summarize ypcf wpopwt
• summarize ylab wpopwt if age gt25 and age
  lt55
• generate new variables
• generate ypc2 ypc2
• tabulate data
• table skill wpopwt, c(mean ylab)

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Some Basic Commands

• renaming variables
• rename ypc2 ypcf22
• eliminating variables
• drop ypc22
• replacing values
• replace male0 if male1

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Open data from Excel format

• Import data from excel file

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Open data from Excel format
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Open data from Excel format
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Review data
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Starting descriptive analysis
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Starting descriptive analysis
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Output Window