How to Create a Unique ID From an ID Variable That Contains Duplicates

This article explains how to use JavaScript to create a unique ID variable from an ID variable that contains some repeated values. In some cases, the data file may be missing a variable that identifies each respondent uniquely because some respondents have data in more than one row of the file, but there is still a need to have a variable that identifies the cases uniquely (for example to set the Case IDs in the data set).

Here, we make a new variable for each occurrence of an ID value after the first has a number appended to it. For example, if the ID 10035 appears twice, the new variable will have values of 100355 and 100355_1 in the corresponding rows.

Note

This process requires you to make a new copy of your SPSS data file. A new data file is necessary because in order to set a variable as a Case ID, the variable must be in the raw data, rather than a constructed variable. Creating a new copy of the data file hard codes the new variable into the raw data.

Please note these steps require a Displayr license.

var _old_ids = CustomerID;

var _new_ids = _old_ids.map(function (x) { return x.toString(); });

_new_ids.forEach(function (_i, _ind) {
    if (_new_ids.indexOf(_i) < _ind) {
        var _counter = 1;
        while(_new_ids.indexOf(_i + "_" + _counter.toString()) < _ind && _new_ids.indexOf(_i + "_" + _counter.toString()) > -1)
            _counter ++;
        _new_ids[_ind] = _i + "_" + _counter;
    }
});
                
_new_ids