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==.
