In RxJava, how to pass a variable along when chaining observables?

The advice I got from the Couchbase forum is to use nested observables:

Observable
    .from(modifications)
    .flatmap( (data1) -> { 
        return op1(data1)
            ...
            .flatmap( (data2) -> { 
                // I can access data1 here
                return op2(data2);
            })
        });

EDIT: I’ll mark this as the accepted answer as it seems to be the most recommended. If your processing is too complex to nest everything you can also check the solution with function calls.