> tapply(growrate,list(gender,bonedev),mean) Severely Depressed Moderately Depressed Mildly Depressed Male 2.0 1.9 0.9 Female 2.4 2.1 0.9 > > tapply(growrate,list(gender,bonedev),length) Severely Depressed Moderately Depressed Mildly Depressed Male 3 2 2 Female 1 3 3 > > dev.off() null device 1 > > >