; dx = physical units per x pixel
; dy = physical units per x pixel

; get pixel units from !p.clip = [x0,y0,x1,y1]
; get physical units from !x.range


pro plotscale, dx, dy

    dx = (!x.crange[1]-!x.crange[0])/float(!p.clip[2] - !p.clip[0])
    if dx lt 1 then $
      dx = (!x.crange[1]-!x.crange[0])/float(1.+!p.clip[2] - !p.clip[0])
      
    dy = (!y.crange[1]-!y.crange[0])/float(!p.clip[3] - !p.clip[1])
    if dy lt 1 then $
      dy = (!y.crange[1]-!y.crange[0])/float(1.+!p.clip[3] - !p.clip[1])
    

end