Working with variables

Creating new variables

Variables are created by the command generate

Syntax:  generate [variablename]

generate [newvar] = [expression]

While creating a vairiable, you can too assign an initial value by use of = operator.

eg generate true=1

generate fullname = last + “, “ + first

Renaming variables

This is done to assign a new variable to an existing variable

Syntax: rename [old name] [new name]

Here I am changing the variable name from “old name” to “new name”

Replacing variable values

when you need to replace the existing values of a variable, the re is provision through the command replace

Syntax: replace [variable name] =[value] [conditions]  [options]

e.g replace true=0 in 1/10 this will replace value of true to 0 for all variables 1 to 10

Recoding variables

suppose you had this data

.tab age

Age	Frequency
18	2
19	6
20	3
21	4

now you want to recode the variable age into age groups, say 18 to 19, 20 to 21

this will be achieved through this command

.recode age (18 19 = 1 “18 to 19”) ///
(20 21= 2 “20 to 21”) ///
(else=.), generate(agegroups) label(agegroups)

As we see, recode helps reorganize data.

.tab age

Age	Frequency
18 to 19	8
20 to 21	7

Labeling variables

to label a variable, first you have to define the label then implement it on the variable.

This is how its done in Stata

Syntax: label define [value/variable] [Lable] …………….

label values [variable] [label]

eg

label define genderlabel 1 male 2 female

label values gendervariable genderlabel

Deleting variables

If you had a temporary variable, or you are doing data cleanup, sometimes its necessary to delete some variables.

Syntax: drop [variable name] [options] Note: If you just execute drop without variable name of options, you will be deleting all variable in the data set

eg. drop age if age==.

Follow @GichureMkenya