Multiple columns of groups caused error in merge.splitByData

[billdenney]

When creating two groups as follows, the error below occurs.

myconc <- PKNCAconc(data=myrawconcdata ,formula= conc~time|subject/analyte)
# Put your dose data into a PKNCAdose object
mydose <- PKNCAdose(data=myrawdosedata ,formula= ~time|subject)
# Combine the two (and automatically determine the intervals of
# interest
mydata <- PKNCAdata(myconc, mydose)

Error in FUN(X[[1L]], ...) (from merge.splitByData.R#25) : 
  2 arguments passed to 'names' which requires 1