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

Stata 11 Sample Session Section 2 – Restructuring Data Files – Table Lookup & Aggregation
The for z in num 1/3 looping
command
The foreach looping command
The levelsof command
2. The dialog box opens. In the New Variable box: type
quart.
3. In the Expression: box type cprod_ae.
4. In the “Options” section, select 4 quintiles.
5. Click on the “If/In tab and in the if: expression type
district == 1.
This command would have to be repeated for the other
two districts so that 3 variables are created where the
observations for that district are divided equally into 4
groups.
Using the “if” expression works where you have only a
few codes within the variable. We have 3 districts so it
would not be a problem to use the if expression. What if
we had 20 districts? This method would be a bit
cumbersome.
Another method is to use a counter. Add the command
“for z in num 1/3” in front of the xtile command, where z
is a temporary variable that loops through the values
specified with the “num 1/3”. The value of 3 would be
replaced with the number of values in the district
variable. Note that the “z” is added to the “quart”
variable and that “z” is used instead of the actual numeric
value for the value to use for the value for district.
for z in num 1/3: xtile quartz = cprod_ae if
district==z, nq(4)
Stata provides another looping command that we can use
to compute the new ranking variable. It is not available
through the menus. The looping command can be found
in the Programming manual and is called foreach. Stata
added a new command called levelsof . The values are
stored in temporary variables called r(levelsof). That
information can be stored in a local variable and the
variable used to cycle through the values.
1. Type the following command in the Command
window:
The results should display the values of the
districts, e.g. 1 2 3
2. Now let’s store that information in a local
variable. To make a temporary local level, we
include the word “local” which means the variable
only exists with the do-file. We need this
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levelsof district