I\'ve been trying to cut down on the amount of copying and pasting required to make a large number of charts with slightly differing functions / slices of the data.
facet_grid() takes a formula object, and you can create a formula object from a string with as.formula(). So you should be able to do something like:
facet_grid()
as.formula()
facet_grid(as.formula(paste(rowfacet, "~", colfacet)))