stata training session 1

7/29/2019 STATA Training Session 1

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Sun LiCentre for Academic Computing

[email protected]

STATA Training Session 1Introduction to STATA
mailto:[email protected]:[email protected]


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Outline Computing Resources

Getting Started with STATA

Running STATA

Datasets in STATA

Data Management with STATA

Exercise 1

Data Descriptions & Simple Graphs

Exercise 2


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Download Training Slides , data and Syntax:

http://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/Training%20Slides%20and%20Syntax.aspx
http://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/Training%20Slides%20and%20Syntax.aspxhttp://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/Training%20Slides%20and%20Syntax.aspxhttp://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/Training%20Slides%20and%20Syntax.aspxhttp://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/Training%20Slides%20and%20Syntax.aspx


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Computing ResourcesSTATA is a statistical package for managing, analyzing, and graphing

data.

has both command and menu-driven interface

has cross-platform compatibility: Windows, Unix, and Mac.

has three flavors:

the standard Intercooled STATA (2047 variables)

the more limited Small STATA (99 variables)

the extended STATA/SE (32766 variables).


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Computing ResourcesCAC Computing Resources for STATA users Windows:

STATA/SE version 10.0

10-user network perpetual license

Installation guide(http://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/STATA-Software Questions.aspx)

LinuxCAC Beowulf Cluster: STATA/SE version 10.0

Unlimited users

About CAC Beowulf Cluster:(http://research2.smu.edu.sg/CAC/HPC/Wiki/MAIN.aspx)

New features in STATA 10.0 (http://www.stata.com/stata10)
http://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/STATA-Software%20Questions.aspxhttp://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/STATA-Software%20Questions.aspxhttp://research2.smu.edu.sg/CAC/HPC/Wiki/MAIN.aspxhttp://www.stata.com/stata10http://www.stata.com/stata10http://research2.smu.edu.sg/CAC/HPC/Wiki/MAIN.aspxhttp://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/STATA-Software%20Questions.aspxhttp://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/STATA-Software%20Questions.aspxhttp://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/STATA-Software%20Questions.aspx


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Getting Started


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Getting Started

Review box

Variablewindow

Command line

Resultswindow


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Getting StartedGetting help in STATA Help menu:

contents : for a list of command categories & language syntax

help : for a STATA command with examples

search: to search help by keywords From command line:

help list

search logistic models

net search multilevel model

User-written programsSJ, STB, STATAlist, and others:

help net_mnu


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Getting Started

Website resources: The STATA website: http://www.stata.com

The STATA journalreviewed papers, regular columns, user-writtensoftware: http://www.stata-journal.com/

STATA FAQ : http://www.stata.com/support/faqs STATA User Support : http://www.stata.com/support Books: http://www.stata.com/bookstore/statabooks.html

CAC STATA support:

Website:

http://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/STATA.aspx Contact:

For statistical consultation: Sun Li: [email protected]

For software installation: TAN SuhWen: [email protected]
http://www.stata.com/http://www.stata-journal.com/http://www.stata.com/support/faqshttp://www.stata.com/supporthttp://www.stata.com/bookstore/statabooks.htmlhttp://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/STATA.aspxmailto:[email protected]:[email protected]:[email protected]:[email protected]://research2.smu.edu.sg/CAC/StatisticalComputing/Wiki/STATA.aspxhttp://www.stata.com/bookstore/statabooks.htmlhttp://www.stata.com/supporthttp://www.stata.com/support/faqshttp://www.stata-journal.com/http://www.stata-journal.com/http://www.stata-journal.com/http://www.stata.com/


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Running STATA Files in STATA

Commands and Output

STATA Variable Definitions

Missing Values in STATA

Expressions and Functions

Memory Consideration


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Running STATAFiles in STATA .dtaSTATA dataset

STATA can read and write from/to ASCII files, such as Excel files.

.doSTATA do-file, command file Do files can be edited and displayed by text editor, like Notepad.

.log, .smclSTATA log file, output file Log files document the commands and analysis results displayed in Result

Window, including error messages. Log files (.log) can be edited and displayed bytext editor.

.gphSTATA graph file


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Running STATACommands and Output Command prompt driven in:

Batch mode: do-file

Interactive mode: command line

E.g.: verinst -- verifying version and installation of STATA


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Running STATA To save results: log-files

File -> Log -> Begin..., View..., or Close.

.smclor .log extension.

Record everything in Results Window, including commands, results, errormessages, etc.

If the file already exists, another dialog opens to allow you to decide whether tooverwrite the file with new output or to append new output to the existing file.

From command:

cd // list current working directorycdD:\lsun // change working directory to be D:\lsun

dir // list files under the current working directory


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Running STATASTATA Variable Definitions Variable names

1-32 characters: recommend to use 8 characters

Valid character: letters a-z, numbers 0-9 and underscore _

Name must be started with a letter (or underscore, but discouraged becauseSTATA-generated variables start with an underscore.)

Case-sensitive: lowercase or uppercase letters

Variable types

String (Storage bytes: Str1 to Str80Str244 in SE)

Numeric (categorical, continuous)


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Running STATA Format of numeric variables

Numeric formula: %w.dg; %w.df; %w.de

w: the total width, including period and decimals

d: number of decimals

Format Formula E xample 2 1,000 10,000,000

General %w.dg %9.0g 1 1000 1e+07

Fixed %w.df %9.0f 1 1000 10000000

%9.2f 1.41 1000.00 1.00e+07

Exponential %w.de %10.3e 1.414e+00 1.000e+03 1.000e+07


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Running STATAMissing Values in STATA

Missing values are created in input or import when a numeric field is empty;or by invalid calculation, e.g. division by zero.

System missing value is shown as a

(period). Or a period followed by aletter, such as . a, . b, etc.

Missing values are interpreted as a very large positive number with:

. < . a < . b < etc

This can lead to mistakes in logical expressions.


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Running STATAExpressions and Functions Operators

Arithmetic Relational Logical^ power > greater than ! not* multiplication < less than ~ not/ division >= > or equal | or+ addition


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Running STATAMemory Consideration When your dataset is very large, you may consider to:

Set the size of memory: set memory

Set the maximum number of variables: set maxvar

Set the maximum dimension of matrices: set matsize

e.g. memory

set memory 64m

Parameter Default Min Max

memory 10M 500K

maxvar 5,000 2,047 32,766

matsize 400 10 11,000


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Getting started: Q & AQ1: Is there a way to stop Result Window breaking output into pages, i.e.how to get rid of thismoremessage and let Result Window roll to

the last line of output?

Hint: command help set to understand system parameters

Q2: Why do I get the error message no room to add more observationseven after I reset STATA memory to load my data set?

Hint: Two important considerations:

1) Make sure that you allocate an amount of memory that is larger than the file thatyou are using. Stata will need the extra room to perform any commands orcalculations.

2 Make sure that you do not allocate too much memory because your computerwill not have enough memory (RAM) left to perform other tasks.


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Datasets in STATA Starting PointA Rectangular Matrix

Data Input and Output

Edit Data Properties

Variable Management

Data Reorganization

Date and Time Values in STATA


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Datasets in STATAStarting Point: A Rectangular Matrix

321

2232221

1131211

...

...............

...

...

NKNNN

K

K

XXXX

XXXX

XXXX

Nobservations

K variables


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Datasets in STATAData Input and Output

Load STATA-format dataset:

use [varlist] [if] [in] [using] [filename] [, clear]

Save data in memory to file:save [filename] [, save_options]

Clean dataset from memory:

clear

Note: STATA is case-sensitive.

All STATA commands are lowercase.

STATA allows only one dataset at one time in memory.


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Datasets in STATA varlist : a list of variables with blanks in between.

var1 just one variablevar1 var2 var3 three variablesvar* variables starting with var*var variables ending with var

var1-var3 var1, var2 and var3 if : conditional language

if mpg>40if mpg>40 & income==70if mpg>40 | mpg


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Datasets in STATA

Import dataset of other formats Stata can import tab-delimited ASCII text files directly.

Excel can write tab-delimited ASCII text files

choose FileSave AsSave as type: Text (tab delimited)

Import text file into STATA

Choose FileImportASCII data created by a spreadsheet


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Datasets in STATAExample

sysuse auto, clear //open system dataset auto.dta and clear any dataset in memory if any

save auto, replace //save the data in memory to working directory and replace if any

describe //describe the dataset

browse //open data browser

edit //open data editor


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Datasets in STATAEdit Data Properties

generate x=price/mpg //create new variable from algorithm

rename x priceunit //rename variable

label variablepriceunit "price per mpg //label variable

listpriceunit in 1/10 //list first 10 obs for the variable priceunit

Edit variable properties from Data Editor in edit mode


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Data Management with STATAVariable Management

recodeprice (10000/max=5 "10000+") ///

(6000/10000=4 "6000-9999") (5000/6000=3 "5000-5999") ///

(4000/5000=2 "4000-4999") (min/4000=1 "-4000") , generate (pricegrp)

label varpricegrp price group

dpricegrp

codebookpricegrp

recodepricegrp (1/2 = 1 "-5000") ///

(3/4=2 "5000-9999") (5=3 "10000+"), generate (pricegrp2)

codebookpricegrp pricegrp2

save auto, replace


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Data Management with STATAgenerate x="F //generate a new variable with value = F

replace x="M" in 20/l //replace value of x =M from obs 20 to the last

encode x, generate (xcode) //convert string variable x to be numeric and save it to a new var

dx xcode

browse x xcode

drop x xcode


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Data Management with STATAData Reorganization

sortforeign //sort dataset by variable foreign

byforeign: summarizeprice //descriptive statistics of price by foreign group

bysortforeign: summarizeprice //alternative way

keepprice pricegrp foreign //keep the three variables and drop the rest

keep in 1/50 //keep the first 50 obs

drop ifprice < 4000 //drop obs if price < 4000

saveprice, replace //save it into a new dataset

Note: sort only sorts inascending order. To sortdescending:

gsortprice -mpg


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Data Management with STATAdir

use hsmale, clear

codebookgender

use hsfemale, clearcodebookgender

append using hsmale

codebookgender

save hsappend,replace

append : to combine the information from twofiles with the same variables but different obs.


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Data Management with STATAdir

use hsdem, clear

sort id

save, replace

use hstest, clear

sort id

merge idusing hsdem

listsave hsmerge

tab_merge

Note: Both files must be sorted beforehand by matching key (id in the example above), and thematching key must have the same name in both datasets.

merge : To combine the information from twofiles with different information about thesame obs.


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Date and Time Values in STATA

sysuse sp500

d

list date in 1/10

generateyear1=year(date)

generate month1=month(date)

ddate year1 month1


How STATA records dates and times:

Dates and times are called %t values. %t values arenumerical and integral. The integral value recordsthe number of time units that have passed from 1960.


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ddate year1 month1 year2 month2

list date year1 year2 month1 month2 in 1

generateyear2=yofd(date)

generate month2=mofd(date)


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Data Management: Q & AQ1: Why does my merge produce a dataset with too many observations?

Q2: How do I create dummy variables?

Q3: How can I list, drop, and keep a consecutive set of variables without

typing the names individually?

Q4:Why does my do-file or ado-file produce different results every time Irun it?

Q5: How do I deal with multiple responses?

http://www.stata.com/support/faqs/data/
http://www.stata.com/support/faqs/data/merge.htmlhttp://www.stata.com/support/faqs/data/dummy.htmlhttp://www.stata.com/support/faqs/data/varlist.htmlhttp://www.stata.com/support/faqs/data/varlist.htmlhttp://www.stata.com/support/faqs/lang/sort.htmlhttp://www.stata.com/support/faqs/lang/sort.htmlhttp://www.stata.com/support/faqs/lang/sort.htmlhttp://www.stata.com/support/faqs/data/multresp.htmlhttp://www.stata.com/support/faqs/data/http://www.stata.com/support/faqs/data/http://www.stata.com/support/faqs/data/http://www.stata.com/support/faqs/data/multresp.htmlhttp://www.stata.com/support/faqs/lang/sort.htmlhttp://www.stata.com/support/faqs/lang/sort.htmlhttp://www.stata.com/support/faqs/lang/sort.htmlhttp://www.stata.com/support/faqs/lang/sort.htmlhttp://www.stata.com/support/faqs/lang/sort.htmlhttp://www.stata.com/support/faqs/lang/sort.htmlhttp://www.stata.com/support/faqs/data/varlist.htmlhttp://www.stata.com/support/faqs/data/varlist.htmlhttp://www.stata.com/support/faqs/data/dummy.htmlhttp://www.stata.com/support/faqs/data/dummy.htmlhttp://www.stata.com/support/faqs/data/merge.html


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Exercise 1


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Brief Introduction of Graphics

Plot area

10

20

30

40

2,000 3,000 4,000 5,000

X-axis title

first legend second legend

Legend

Note: This is the outer region or background

Subtitle: The anatomy of a graph

Title: Figure 1


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Brief Introduction of Graphicssysuse auto, clear

twoway(scattermpg weight ifforeign==0, msymbol(diamond) mcolor(green))

(scattermpg weight ifforeign==1, msymbol(diamond) mcolor(red)),

title(Title: Figure 1) subtitle(Subtitle: The anatomy of a graph)

ytitle(Y-axis title) xtitle(X-axis title)

note(Note: This is the outer region or background)

legend(title(Legend) label(1 first legend) label(2 second legend))

text(35 3400 "Plot area")


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Data Description & Simple GraphsDescribing Datasets

use auto, clear

describe


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Data Description & Simple GraphsDescribing Variables

codebook

summarizeprice mpg weight length

summarizeprice mpg, detail

bysortforeign: summarizeprice mpg

Command summarize: providesdescriptive statistics with option fordetails.


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Data Description & Simple Graphshist weight,frequency normal

hist weight,frequency normal start(750) width(250) label(1000(500)5000)

0

5

10

15

2,000 3,000 4,000 5,000Weight (lbs.)

0

5

10

15

1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000Weight (lbs.)


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Data Description & Simple Graphsgraph box mpggraph box mpg,over(foreign)

graph bar(mean) mpg trunk,over(pricegrp) ///

legend(label(1 "mpg") label(2 "trunk")) ///

blabel(bar, position(inside) format(%9.1f) color(white))

10

20

30

40

Domestic Foreign

26.2

10.5

22.5

12.8

20.6

15.4

20.4

14.5 15.0

16.6

0

5

10

15

20

25

-4000 4000-4999 5000-5999 6000-9999 10000+

mpg trunk


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Data Description & Simple GraphsTabulating Data

tab1foreign pricegrp

tab2foreign pricegrp

tab2foreign pricegrp, row column

Command tab1: provides one-wayfrequency table.

Command tab2: providescontingency table.


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Data Description & Simple Graphstab1foreign, summarize(price)

tabstatprice mpg, by(foreign)

tabstatprice mpg, stat(n mean sd p25 p50 p75) by(foreign)

Command tab1: tabulates descriptivestatistics for continuous variables.

Command tabstat: displays table ofsummary statistics.


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Data Description & Simple Graphsgraph pie, over(pricegrp)graph pie, over(pricegrp)plabel(_all percent, color(white)) by(foreign)

13.46%

42.31%17.31%

11.54%

15.38% 18.18%

18.18%

22.73%

31.82%

9.091%

Domestic Foreign

-4000 4000-4999

5000-5999 6000-9999

10000+

Graphs by Car type

-4000 4000-4999

5000-5999 6000-9999

10000+


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Graphics: Q & Ahttp://www.stata.com/support/faqs/graphics/

Exercise 2
http://www.stata.com/support/faqs/graphics/http://www.stata.com/support/faqs/graphics/http://www.stata.com/support/faqs/graphics/


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Next SessionStatistical Analysis

17 Oct Friday, 9.30am-12pm

Training Room @ Library Level 5

Data Description And Simple Inference

Group Comparison And Correlation

General Linear Regression

Logistic Model

Binary Logistic Model

Ordinal Logistic Model

Multinomial Logistic Model

stata training session 1

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