STATA 11 for Windows SAMPLE SESSION - Food Security Group ...

Stata 11 Sample Session Section 1 - Basic functions: Files, Descriptives, Data Transformations
Data Transformations After examining the results of the descriptive statistics you
will often want to do data transformations. A data
transformation is an operation that takes an existing variable
and either changes the values in a systematic way or uses
the values to calculate a new variable. The following
example shows a common data transformation: the
conversion of a continuous variable to a categorical
variable.
Converting continuous
variables to categorical
variables
The generate command
The replace command
The label variable command
The label define command
First method:
The generate command
The information we received from the summarize
command is interesting, but it might also be useful to see
the actual distribution of the ages into groups or categories,
so we can tell, for example, how many heads of household
are older than 60. Since the age variable, ca3, is
continuous, we cannot do this directly—first we have to
transform it. Let's suppose we're interested in four
categories: 0-10 years old, 11-19 years, 20-60 years, and
over 60 years of age.
To categorize a variable, we can use the generate
command. Categorizing a continuous variable makes
detailed information more general. To keep the detailed
information as well as the new general information, you
must recode the variable into a new variable. If you recode
into the same variable the original values will be lost.
There are several methods that can be used to recode a
continuous variable.
First method: If you wish to see the category values of 1,
2, 3, and 4 where
1 = 0-10,
2 = 11-19,
3 = 20-60 and
4 = over 60
you can do the following:
1. From the Data menu select Create or change
variables / Create new variable
The Generate - Create a new variable dialog box opens.
2. Under the Main tab, type the name of the new
variable in the Variable name box: age_gp
3. For the Contents of new variable box, type in
1
This is the value that you want the new variable to have.
4. In the drop down box for the Variable type select
byte.
5. Click on the If/In tab.
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