In Stata, how can I randomly select a certain number of observations from a data set?

In Stata, the .sample command selects random samples of the data set in memory and removes unselected observations from the data set.

Suppose you want to randomly draw a sample of 100 observations from the current data set. First, load a data set, and then run the following command with the count option:

If you want to take a sample of 20% from the current data set, drop the count as follows:

If you want to take a sample that maintains the same proportion of each group, use the by() option. The following command selects 20% observations within male (male=1) and female (male=0) groups.

.sample draws a sample without replacement. If you want to allow replacement, use the .bsample command instead.

For more about statistical and mathematical software, email the UITS Stat/Math Center, visit the center's web page, or phone 812-855-4724 (IUB) or 317-278-4740 (IUPUI). The center is located in Bloomington at 410 N. Park Avenue, and is open for consultation by appointment Monday-Friday 9am-5pm.

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