Introduction to
gretl
Outline
1 What is gretl?
2 Installing gretl
3 Importing Data
Saving as gretl File
5 Running a Script
6 FirstExercises
7 Commands on Datasets
8 Commands on Variables
9 Graphs
4
What is gretl?
What is gretl?
• gretl is an acronym for Gnu Regression Econometrics and
• Time-series Library
• it is free econometricssoftware
• it has an easy Graphical User Interface (gui)
• it runs least-squares, maximum-likelihood, systems estimators... it
outputs results to several formats
• veryimportant for us in this course: it admits scripts (sequence of
commands saved in a file)
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What is gretl?
Howdo I get gretl?
Handy for remote learning since it is open-surce free software anyone
can install it on home desktop without the need of license
In order to install it go to:
http://gretl.sourceforge.net
It runs on Windows, Mac, Linux
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Installation
• Open the webpage and go down where Download section is located.
Click on the circled button for windows users
Installation
• Choose the .exe file which is appropriate for your system
Installation
• Run the .exe file and choose default options to proceed. Do not
forget to add gretl directory to your PATH
Start gretl
• To start gretl you can just type gretl in your search button.
Select it and an empty gretl window will pop out. You can
either run commands directly in the gretl console or write
scripts and save them for future use
Gretl
console
Gretl
scripts
What is gretl?
Howdo Iworkwith gretl?(1/2)
• the easiest way for beginners is by using its graphical userinterface
• you can also use the console button of the toolbar: from the prompt
(?) you can execute gretl commands one line at a time.
• the most efficient way is by usingscripts:
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create a script file, write gretl commands one every line, and save it
run the script using the gui
inspect output
if needed, change script file, save it, and go back to step 2
Running commands in the script
• Click CTRL + R or click the button shown below. The window with
outputs (or errors) will open. If you save these scripts, it will be
saved as .inp file.
What is gretl?
Howdo Iworkwith gretl?(2/2)
you know your way using the gui,but want to know about scripts...
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actions you do with the gui are stored as script in a filed called
session.inp
gretl comes with over 70 practice scripts
the manual gives good advice and devotes several chapters to provide
good programming solutions
this course willprovide you with tested scripts
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Opening datasets
❑ Gretl comes with inbuilt datasets which you can play with
❑ Go File -> Open data -> Sample file and this will give you lots of
datasets, or alternatively, go to specific data file which you
want to access in your computer by choosing User file instead
of sample file
Opening datasets
❑ If you want to open file which has a different extension, for example
excel, when you go to User File, do not forget to set it for excel
searching, otherwise nothing will be shown in the window
Opening datasets
❑ For now let’s open a Sample file the very first one offered ‘abdata’
by double-clicking it with a mouse
Playing with data
• The following window will pop out. You can now check the values of
each variable by double clicking them. You can edit them etc.
Operations on variables
❑ See summary statistics of variables by highlighting them and
clicking Variable -> summary statistics in the upper panel
❑ Change values of variables by highlighting it and clicking Data ->
Edit values
Saving as gretl File
Saving as a new gretl File
You can open any other type of file using gretl (excel), do some operations on them
and then save as a gretl file (.gdt) by clicking: File -> Save Data as -> Standard
format
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Running a Script
Looking at the Session Script
Tools > Command log displays the operations that we have done so far. It is
recorded only if we run the commands from the console or GUI. If we run them
from the script, logs won’t record them
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Running a Script
Moreon scripts
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using File/Script files/New script you open the command script editor
If you have a very long command that exceeds one line, use the
backslash (\) as a continuation command
using scripts (and the console) requires you to use the correct
language syntax
gretl's language is case sensitive: gretl considers x to be different
from X
you can find all the commands in the gretl command reference after
clicking Help -> command reference
at the console window, you can type help
First Exercises
Exercise 1
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• Load the file engel.gdt. The data set contains two variables named
income and foodexp. The variable foodexp is annual expenditures on food
in a household and income is annual income measured in $100
increments.
• Using GUI, add natural logs of both variables.
• Using GUI, summarize foodexp for households with income below the
median.
• Using GUI, plot foodexp againstincome.
• Write all the commands in a script file and save it.
• Open the script and run the commands.
• Save the new dataset.
First Exercises
Exercise 2
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The file bweight.xlsx contains information about infants' birth weight, sex
and race, the income of their faimilies, their parents' education and the
number of cigarettes the mother smoked per day during pregnancy (msmoke).
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Import from gretl the file bweight.xlsx
Compute the average birth weight for all the babies in the sample, and
separately for boys and girls.
Compute the proportion of mothers that smoked duringpregnancy.
Which familiy variables do you think are related to children's birth
weight? Compute the correlation among bweight and those variables.
Save the new database in gretl format.
Write down all the previous commands in a script and save it. Close
your session, open the script and run all the commands together.
First Exercises
Basic commands for data management (1/2)
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Commands on the entire data
open: opens a data file replacing any data file already open
smpl: defines the sample range
dataset: sorts/clears/transposes/adds observations and more
setobs: declares the structure of the data (cross-section, time-series,
panel)
append: appends the content of a data to the current dataset
store: saves the data into a file
First Exercises
First Exercises
Basic commands for data management (2/2)
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Basic commands on variables
genr: creates a new variable
delete: removes variables
setinfo: sets attributes of a variable
rename: renames a variable
summary: shows summary statistics for variables
print: lists the values of variables
First Exercises
Commands on Datasets
open dataname −−www −−sheet= "name"
−−coloffset=# −−rowoffset=#
opens a dataset replacing any already loaded data
−−www opens database in gretl server
with spreadsheets, it selects the worksheet, and the first column and
row
the first row must contain valid variable names. In the case of an
ASCII or CSV import, if the file contains no row with variable names
the program willautomatically add names, v1, v2 and so on.
open C:\there\mydata.xls −−sheet= mysheet −−coloffset=3
−−rowoffset=2
opens worksheet mysheet from C:\there\mydata.xls
reads the data from the fourth column and thirdrow
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Commands on Datasets
smpl (#start #end | condition −−restrict | #
−−random | full) −−replace −−balanced
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condition −−restrict: restricts the sample to observations that satisfy
the condition
# −−random: # cases are ramdomlyselected
full: restores the full data range
sample restrictions are by default cumulative: −−replace turns o f f all
previous restrictions
Examples
smpl YEAR!=1976 −−restrict
smpl EMP > 3 −−restrict −−replace
smpl 50 −−random
Commands on Variables
rename varname newname
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changes the name of the variable
names must be of 15 characters maximum
they must start with a letter
they must be composed of only letters, digits, and the underscore
character
Example inbwght.gdt
rename bweight birth_weight
Commands on Datasets
dataset (addobs # | transpose | sortby varname |
resample # | clear)
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addobs: adds extra observations at the end
transpose: transposes current data set.
sortby: sorts data by varname (dsortby: descending order) (a list of
variables can be provided; available only for undated data).
resample: random sampling (Constructs a new dataset by random
sampling, with replacement, of the rows of the current dataset. The
original dataset can be retrieved via the command smpl full).
clear: clears out current data
Examples
dataset sortby msmoke
dataset resample 500
dataset clear
Commands on Datasets
setobs #freq #start (−−cross-section | −−time-series |
−−stacked-cross-section | −−stacked-time-series)
#freq represents frequency in time-series data
in panel, #freq is units in stacked cross-sections or periods in stacked
time series
for cross-sections, #freq=1
#start=1 for panels and cross-sections in
time series, #start is the starting date
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Commands on Datasets
setobs unitvar timevar −−panel-vars
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imposes a panel interpretation
sorts data as stacked time series, by ascending values of unitvar
Examples
setobs 1 1 −−cross-section
setobs 20 1:1 −−stacked-time-series
setobs unit year −−panel-vars
Commands on Datasets
append newdata −−time-series
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opens a data file and appends the content to the current dataset
First case: additional observations for existing variables
Second case: new variables (best if # obs compatible)
Third case: appends a time series in a panel
First Case
open C:\there\Example2.xls −−sheet= first100
append C:\there\Example2.xls −−sheet= moreunits
appends worksheet moreunits fromC:\there\Example2.xls
Second Case
append C:\there\Example2.xls −−sheet= wages
appends worksheet wages from C:\there\Example2.xls
Commands on Datasets
append
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Third Case
You have a panel and you want to add a variable which is available in
time-series form. For example, you want to add annual CPI data to a
panel in order to de ate nominal income gures.
open the data: C:\there\Example2.xls −−sheet= first100
you need to have a panel: setobs unit year panel-vars
append C:\there\Example2.xls −−sheet= cpi
Commands on Variables
[genr] newvar = formula
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a formula is a well-formed function ofvariables
the range over which the result is written depends on the current
sample
arithmetical operators: ^, *, /, + , boolean
operators: ! (negation), && (AND), || (OR), >, <, =, > = ,
< = , !=
look at the gretl Function Reference (Help/Function Reference) for
built-in functions
Examples
genr y = 3 + 2 * x1 + 5 * x2 + error
D1976 = (YEAR = 1976)
genr avgy = mean(y)
Commands on Variables
delete [varlist ] −−db
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removes listedvariables
if no varlist is given, it deletes the last (highest numbered) variable
from the dataset
−−db: deletes variables from a gretl database
Commands on Variables
setinfo varname −d "thislabel" −n "thisname" −−discrete
−−continuous
−d "thislabel": thislabel is set as the variable's descriptivelabel
−n "thisname": thisname is used in place of the variable's name in
graphs
−−discrete: marks variable as discrete (by default variables are
continuous)
Examples
setinfo x1 −d "Description of x1" −n "Graph name"
setinfo z−−discrete
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Commands on Variables
print [varlist] −−byobs −−no-dates
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prints the values of the variablesin varlist
if no list is given, prints the values of all variables
−−byobs: data are printed by observation, not by variable
you can also printstrings
Examples
print bweight male −−byobs
print bweight ; male −−byobs
print "This is a comment"