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

Stata 11 Sample Session Section 2 – Restructuring Data Files – Table Lookup & Aggregation
Calculate the adult equivalents
for the household
The collapse command
codes are all "average" individuals, and assign them the
adult-equivalent value of .79. (Warning: be very cautious
about "filling in" missing data this way. Careless use of
this technique can give you misleading results. We are
using this example to illustrate the use of Stata commands
and not recommending that you do this routinely to
compensate for missing data.)
We will use the Replace command to change the system
missing values (.) in the ae variable to .79.
1. Data then Create or change variables then
Change contents of variable
The replace - Replace into same variable dialog box
will appear.
2. Under the Main tab, select ae in the Variable:
box
3. In the New Contents box type .79
4. Under the if/in tab in the Restrict to
observations if: box type
ae==.
The “period” represents system missing.
5. Don’t forget to copy the command into the do-file
editor, then click on the Ok button.
6. Check the results of your replace command by
rerunning the tabulate command.
You should see 9 cases in the frequency with a value of
.79.
The Stata commands are:
replace ae = .79 if ae==.
tabulate ae, missing
Now we need to calculate the number of adult equivalents
for each household. The current file is at the member
level, but we need values at the household level. Again
we use Collapse to go from the member level to the
household level. The new variable ae will be calculated
by summing ae across all members of a household.
Reminder: The Grouping variable(s) specify the
variables to be used for combining cases in the collapsed
file. Any cases from the original file that have identical
values for all of the grouping variables will be combined
into a single case in the collapsed file. We want the
collapsed file to have one case per household, so we use
the variables that identify a household in our survey—
district, vil, and hh.
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