Sometimes data do not meet the assumptions of a particular statistic because the data are at the wrong level (e.g., ordinal instead of nominal). In this case, transform these data to the proper type, but only if you transform them from some higher level of data (e.g., interval) to some lower level (e.g., nominal). In other words, while it is possible to transform interval data into ordinal data, it is not possible to transform ordinal data into interval data. 

This type of data transformation will inevitably cause a loss of precision.

For short data files, write in a new column of data manually. For longer data files, use the statistics program to handle the transformation. To explore SPSS' capacity to transform data, click "Transform" and explore.