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

Stata 11 Sample Session Section 2 – Restructuring Data Files – Table Lookup & Aggregation
prod unit conver
(Product) (unit) (conversion factor)
... ... ...
7 8 19
7 24 53
... ... ...
30 8 17
30 24 47
... ... ...
• calories.dta: This also is a table-lookup file, created
for convert kilograms of food into calories of food. It
contains two variables:
a. prod - the product (crop)
b. calories - number of calories per kilogram of
each of the crops
To create a data files that will produce the output table
described above, we need to combine the data from different
files. There are different methods that can be used to combine
files, depending on what is desired. In Stata, we can
1. Append datasets. Appending data sets means that
the data in different files have the same variables
and the desire is to add one data set of
observations to the end of another data set (or
append one file to the end of another file). An
example would be that you entered data for
harvest in one file for one district and entered data
for harvest for another district into another file.
We want the data to be in the same file. To do
that, we would use the append command.
2. Merge datasets. Merge combines datasets
horizontally matching corresponding observations.
An example is a survey asking questions about the
household in Part 1 and another set of questions
about the household in Part 3. Each part of the
survey is entered into a different data file. To
combine Part 1 and Part 3 (where both sets of data
are at the household level), we would use the
merge command.
3. Joinby datasets. This type of merge combines
datasets horizontally matching all pairwise
combinations possible. An example is a set of
data on parents and a set of data on children.
Joinby would match the parents to every
observation of the children within that family.
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