You can still use this function in SQL scripts, and insert SQL codes into RapidMiner for in-database SQL execution. (need “Read Database” or “Execute SQL” operators)
In rapidminer you can combine several operators for the same operation. For example, “Filter Examples” to remove the missing values (NULL), and then “Filter Example Range” to pick the 1st element.
I am attaching the example process here. Let me know if you have further questions.
Example with the Labor-Negotiations dataset and Generate Attributes:
if(missing([wage-inc-2nd]), -1, [wage-inc-2nd])
if(missing([wage-inc-2nd]), if(missing([wage-inc-3rd]), -2, [wage-inc-3rd]), [wage-inc-2nd])
Not as clean as coalesce() but not bad either.