Why command grid.points(c(0,1,1.1),c(0,1,1.1),vp=viewport(w=0.5,h=0.5,x=0.5,y=0.5,clip=TRUE)) does not clip points (point (1.1,1.1) is still visible), although there is no problem with grid.lines(...)? And one more question - how can I swap direction of tick marks on grid.x(y)axis to turn it inside plot?