These are the packages that would be merged, in order:

Calculating dependencies ...

!!! Problem resolving dependencies for =sci-electronics/gwave-20190116-r100
 done!
Dependency resolution took 0.82 s (backtrack: 0/20).


!!! The ebuild selected to satisfy "=sci-electronics/gwave-20190116-r100" has unmet requirements.
- sci-electronics/gwave-20190116-r100::gentoo USE="-gnuplot -plotutils" GUILE_SINGLE_TARGET="-2-2"

  The following REQUIRED_USE flag constraints are unsatisfied:
    guile_single_target_2-2

  The above constraints are a subset of the following complete expression:
    exactly-one-of ( guile_single_target_2-2 )