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

Stata 11 Sample Session Section 2 – Restructuring Data Files – Table Lookup & Aggregation
STATA 11 - SAMPLE SESSION
SECTION 2 - Restructuring Data Files - Table Lookup & Aggregation
Restructuring Data Files For some types of analysis the data files may need to be
restructured to a different level. The data from the four
sections of the questionnaires—household, member,
production and sales—are in four separate data files
because the data are at different levels. The household
data is at the most general, or highest, level - one case per
household. The other three files contain more detailed
data, which is usually thought of as being at a lower level
- there are multiple cases per household. If you are not
familiar with the concept of levels of data, read
"Computer Analysis of Survey Data -- File Organization
for Multi-Level Data" by Chris Wolf, before continuing
on with this section. This paper is available at
http://www.aec.msu.edu/fs2/survey/index.htm
The analysis we did in Section 1 was done at each level
separately, using just the variables in a single file at a
time. However, other types of analysis require
combining data from more than one file. Let's look at an
example.
Suppose we want to create a table of calories per adult
equivalent produced per day from the principal food
crops. Furthermore, we want to see how this varies by
district and calorie-production quartile.
TABLE:1 Food Production in calories per adult equivalent per day
Calorie Production Quartile
Districts 1 2 3 4
Monapo
Ribaue
Angoche
The data in their current form cannot produce this table.
Many transformations are required to restructure the data
to be able to provide the results for this table. The above
table is an example of the complications you will
encounter in real-world data analysis. This entire section
will be devoted toward the goal of creating this table.
To begin, let's look at the files we have and at the
variables we need to use from each of these:
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