In Stata, how do I detect duplicate observations in a data set?

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)

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