Stat Computing > Stata > Notes

Stata Class Notes
About the Dataset

1.0 Stata commands in this unit

Again, we will not be showing all of the options for any of the commands.

. list
describe
codebook
display
inspect

if exp qualifier
in range qualifier

2.0 Demonstration and Explanation

. list
list female ses read science

The list command without any variable names displays values of all the variables for all the cases. list with variable names displays values only the variables following the command.

Note about --more--
Stata displays --more-- whenever it fills up the computer screen. Pressing the 'space bar' will display the next screen, and so on, until all of the information has been displayed. To get out of --more--, you can click on the 'break' button, select 'Break" from the pull-down 'Tools' menu, or press the 'q' key.

. list female ses read science if science==.
list female ses read science if ses=="high"
list female ses read science if ses==3

The if exp qualifier allows you to list values for those cases for which the exp is "true." The first list displays all cases for which science is missing. Stata uses "." to indicate missing values. The if ses=="high" does not work because ses is a numeric variable. And that is why if ses==3 does work.

Logical operators used in Stata

list female ses read math in 50/60
list female ses read math in f/10
list female ses read math in -10/l

The in range qualifier allows you to list values for the subset of cases in the range. The range f/10 is the same as 1/10 and -10/l is the same as 191/200.

. describe

describe displays a summary of a Stata dataset, describing the variables and other information.

. codebook
codebook female ses race

codebook displays information about variables' names, labels and values.

. inspect female ses race

inspect displays information about the values of variables and is useful for checking data accuracy.

. summarize math
display 9.368^2

This use of display functions as a calculator.  We found the standard deviation of math to be 9.368, and we use the display command to get the variance (the square of the standard deviation).

2.2 Remarks about if and in qualifiers

The if and in qualifiers work with almost all Stata commands. See how these commands from Unit 1 work with the qualifiers.

. summarize read write math if ses==3
correlate read write math in 50/150
graph read math if female==0
tabulate ses if read>50
tabulate ses female in 1/60

3.0 Try the commands on your own

. list
list female ses read science
list female ses read science if science==.
list female ses read science if ses=="high"
list female ses read science if ses==3
list female ses read science in f/10
list female ses read science in -10/l
describe
codebook female ses race
display 27.8^3.2
display (57.5 - 52.23)/10.25294

4.0 Can you answer these questions?

1. What cases have a math score greater than 71?
2. What is the race for those cases in which science is missing?
3. What can you find out about the variable schtyp?
4. What is two to the tenth minus one?

5.0 For More Information

• Statistics with Stata 5 (recommended text). 
  Chapter 2 (especially pages 11-17)
• Stata Learning Modules
  Descriptive Information and Statistics
  Using if with Stata Commands