How do I create an index, ID or key variable?

First situation

Question

I would like to create a new variable (an ID variable) which would number each case in my data, starting with 1 and ending with n, the number of cases in the file. How can I do that?

Answer

- Using syntax: COMPUTE id=$CASENUM.(If nothing happens, select TRANSFORM>RUN PENDING TRANSFORM)

- Using the menu: select TRANSFORM>COMPUTE then enter id in the Target Variable text box and $casenum in the Numeric Expression text box. Click OK.(If nothing happens, select TRANSFORM>RUN PENDING TRANSFORM)

Note that $CASENUM is a system variable. The easiest method to find the list of all system variables is to open SPSS Help and search for "$casenum".

Second situation

Question

What if I do not have any data in my data file but I would still like to create an ID variable with values between 1 and 10.

Answer

This cannot be done using the menu, you need syntax:

- Using syntax:

INPUT PROGRAM.
LOOP id=1 TO 10.
END CASE.
END LOOP.
END FILE.
END INPUT PROGRAM.
LIST.

Third situation

Question

I have many cases with the same ID and would like to create a new variable where I would number consecutively those cases (within each ID).

Answer

See the syntax "Number consecutively cases with the same id.sps".

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