Thanks a lot to David and William - I think ggplot( data=ddd, aes(x=pH, y=BC,group=interaction(type,pH), col=type))+geom_boxplot() was very helpful! All best Troels Den 18-05-2021 kl. 02:27 skrev David Winsemius: > ggplot( data=ddd, aes(x=pH, y=BC,group=interaction(type,pH), > col=type))+geom_boxplot()