1. Housekeeping: Variable labels, value labels, calculations and recoding
Session 2
Housekeeping:
Variable labels, value labels, calculations and recoding

2. Review You have used Stata We hope you found it (surprisingly?) easy
Largely through the menus and dialogues
But also with a few commands
We hope you found it (surprisingly?) easy
Discuss
what you liked
And difficulties so far

3. Housekeeping tasks By housekeeping, we mean This includes:
the small jobs to organise and add labels to the data
They make life easier later.
This includes:
labelling and adding notes to datasets;
labelling variables
labelling categories (or values) taken by the variable
recoding variables and dealing with codes for missing values
using log files to keep a record of what you have done.

4. Labels and notes Use Data  Labels  Label dataset
Open the file named E_HouseholdComposition.dta
Use Data  Labels  Label dataset

5. Dialogue for labelling data set
Type in dialogue as below or use the command
label data “Young Lives Study……” 4

6. Labelling variables Use the menu sequence
Data  Labels  Label variable as shown below
Or type the command:
label variable relcare "What is your relationship to child?“

7. Defining value labels
Use:
Data  Labels  Label values
 Define or modify value labels
and complete the dialogue box that follows.
The corresponding commands show that two steps are needed to label the values.
First, a label must be defined,e.g.
label define sexlabel 1 "male" 2 "female"
Then this label is attached to the variable,
e.g. for the variable called sex use the command
label values sex sexlabel

8. Your turn Work through Section 4.1of the Stata Guide
Note down any difficulties you have and clarify your difficulties with a resource person

9. Recoding a variable Data  Create or change variables
Also use options to define a new variable
Data  Create or change variables
 Other variable transformation commands
 Recode categorical variable

10. Information on the recoded variable
Always safer to recode into a new variable, e.g. seedad2.
The effect of the recoding can be seen by typing
codebook seedad2
If seedad is later no longer needed, it can be dropped.
Use File  Save, to save information on the new variable in the data set.

11. Your turn again Work through Section 4.2 of the Stata Guide
Note down any difficulties you have and clarify your difficulties with a resource person

12. . is less than .a Missing values Symbols for missing values in Stata:
. and .a .b .c and so on, up to .z
These are used to distinguish between the different reasons for values to be missing.
When making calculations, comparisons or sorting, the following rules are observed:
all non-missing numbers are less than .
. is less than .a
.a is less than .b, and so on, up to .z

13. Memory The initial memory in Stata is 1 megabyte
This can be changed, but first type Clear to clear memory
To increase the current memory to 20 mbytes, type
set memory 20m
For setting Permanent memory, use
set memory 20m, permanently
For problems processing large datasets, use the compress command.

14. Log files To keep a record of the output, while using Stata
Open a log file by clicking on the Log icon.
This opens a dialogue
In your working directory
so you can name the log file
It suggests an extension smcl
.smcl stands for Stata Markup and Control Language.
Log files in Stata record both commands and output.

15. Remarks
You can change the extension to “log” to produce a simple ASCII file
Other packages use the idea of a log file to record just the command – not the output as well
You can do this in Stata (but not from the menus)
Notice that the command Stata used for its log file was
. log using “name of file”
Do the same again, but using
. cmdlog using “name of file”
If at a later stage you need to append or replace this file, add the option replace or append at the end of the above commands.

16. Your turn
Practice the above ideas by working through Sections 4.6, 4.7, 4.8 of the Stata Guide.
Then either read your own data into Stata
and perform some simple analyses using methods covered so far
Or use a dataset suggested by the resource persons.

17. So if you have a dataset…
Open, within Stata, the data file in Stata format that you created in the previous session.
Identify the key variables in your data set and set up labels for each of these variables.
Identify any categorical variables in your data set. Then define, and set value labels that describe the levels for each categorical variable.
Finally, re-save your data file.