Monday, September 19, 2011

STATA: Capturing information in labels

Been quoit for awhile, here is a tip on using and getting variable and value labels

Labeling variables and values is useful for understanding what your underlying data represents. This is great while you are in the STATA environment. But many times you may want to use this information in more dynamic ways.

For example, lets say that I am using the autos database and I want to output a simple table of frequencies that looks like this:

Car type    Freq. 
Domestic    52 
Foreign     22 

 In order to do this I have to get the information stored in my variable labels and value label, so follow along:

set more off 
sysuse auto 
label list 

tempname my_table file open `my_table' using ///
"c:\my_table.xls", write replace 

** This is where I get the variable label  ** 
** in long hand                            **  
** local var_name : variable label foreign ** 
local var_name : var l foreign 

** Now that this is in a local   **
** I can use it anywhere         **
** so let's write it to our file ** 
file write `my_table' ("`var_name'") _tab ("Freq.") _n 

** Now lets get our frequencies   **
** and value labels First get the ** 
** name of the label value        ** 
local nm_label : val l foreign 

 forvalues x=0(1)1 { 
        quietly sum foreign if foreign == `x' 
       ** Now to get the label values      **
       ** for 0 "Domestic" and 1 "Foreign" ** 
       ** in the value label origin        ** 
       local val_name : label `nm_label' `x' 
       file write `my_table' ///
         ("`val_name'") _tab (r(N)) _n 

 file close `my_table' 

 This is a powerful way to export data in a meaningful fashion and can save you a lot of time. Recall that after the sum, there are a number of values that we can recover. Type return list, if you need other descriptive statics use the detail option for the sum command. Also you can get post regression estimates through ereturn list after you run a regression. If you are familiar with using matrices in STATA then you can get all of your coefficents, etc.

 More on that later

 Happy coding monkeys...

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