![](https://secure.gravatar.com/avatar/23fd5fd7c9582675882a5336e1927a44.jpg?s=120&d=mm&r=g)
It works. But how to choose not to avoid this problem (/10 or /20 or ....) ? Another little problem: if I use " setbounds currentpicture to boundingbox (((xmin,ymin) --(xmax,ymax)) scaled u) ; " the images are not adjusted to the BoundingBox. So I'm back to my original idea. Fabrice
\midaligned{% \startcombination[4*1] {% \startMPcode input hvdm; l:=2.8mm; r:=0.6; alfa:=45; beta:=0; gamma:=0; defineDefaultArrow (l, r, alfa, beta, gamma); numeric xmin, xmax, ymin, ymax; xmin := -2; xmax :=4; ymax :=5 ;ymin:=-1; u := 0.7cm; pickup pencircle scaled 1pt ; drawarrow ((xmin,0) -- (xmax,0)) scaled u; drawarrow ((0,ymin) -- (0,ymax)) scaled u; draw tightfunction ("x", "-2*(x-1)*(x-1)+2", xmin, xmax, (xmax-xmin)/20) scaled u; path screen; screen=(xmin,ymin)*u--(xmax,ymin)*u--(xmax,ymax)*u--(xmin,ymax)*u--cycle; clip currentpicture to screen; \stopMPcode }{1.} {% \startMPcode input hvdm; l:=2.8mm; r:=0.6; alfa:=45; beta:=0; gamma:=0; defineDefaultArrow (l, r, alfa, beta, gamma); numeric xmin, xmax, ymin, ymax; xmin := -2; xmax :=4; ymax :=5 ;ymin:=-1; u := 0.7cm; pickup pencircle scaled 1pt ; drawarrow ((xmin,0) -- (xmax,0)) scaled u; drawarrow ((0,ymin) -- (0,ymax)) scaled u; draw tightfunction ("x", "0.5*(x-1)*(x-1)+2", xmin, xmax, (xmax-xmin)/20) scaled u; path screen; screen=(xmin,ymin)*u--(xmax,ymin)*u--(xmax,ymax)*u--(xmin,ymax)*u--cycle; clip currentpicture to screen; \stopMPcode } {2.} {% \startMPcode input hvdm; l:=2.8mm; r:=0.6; alfa:=45; beta:=0; gamma:=0; defineDefaultArrow (l, r, alfa, beta, gamma); numeric xmin, xmax, ymin, ymax; xmin := -2; xmax :=4; ymax :=5 ;ymin:=-1; u := 0.7cm; pickup pencircle scaled 1pt ; drawarrow ((xmin,0) -- (xmax,0)) scaled u; drawarrow ((0,ymin) -- (0,ymax)) scaled u; draw tightfunction ("x", "-0.5*(x-1)*(x-1)+2", xmin, xmax, (xmax-xmin)/20) scaled u; path screen; screen=(xmin,ymin)*u--(xmax,ymin)*u--(xmax,ymax)*u--(xmin,ymax)*u--cycle; clip currentpicture to screen; \stopMPcode } {3.} {% \startMPcode input hvdm; l:=2.8mm; r:=0.6; alfa:=45; beta:=0; gamma:=0; defineDefaultArrow (l, r, alfa, beta, gamma); numeric xmin, xmax, ymin, ymax; xmin := -2; xmax :=4; ymax :=5 ;ymin:=-1; u := 0.7cm; pickup pencircle scaled 1pt ; drawarrow ((xmin,0) -- (xmax,0)) scaled u; drawarrow ((0,ymin) -- (0,ymax)) scaled u; draw tightfunction ("x", "2*(x-1)*(x-1)+2", xmin, xmax, (xmax-xmin)/20) scaled u; path screen; screen=(xmin,ymin)*u--(xmax,ymin)*u--(xmax,ymax)*u--(xmin,ymax)*u--cycle; clip currentpicture to screen; \stopMPcode} {4.} \stopcombination}