Detect duplicate observations in a data set in Stata

You can check for duplicate observations in Stata in the following ways:

• The isid command can detect duplicate observations:

  . isid x1 x2 x3

• The duplicates command can list and flag duplicate observations. The list subcommand lists the duplicate observations:

  . duplicates list x1 x2 x3

• The tag subcommand and the generate() option flag duplicate observations by assigning 1 to duplicacy in the variable duple:

  . duplicates tag x1 x2 x3, generate(duple)