grid.add(gPath, child, strict = FALSE, grep = FALSE,
         global = FALSE, allDevices = FALSE, redraw = TRUE)addGrob(gTree, child, gPath = NULL, strict = FALSE, grep = FALSE,
        global = FALSE, warn = TRUE)
setChildren(x, children)
grid.add this
    specifies a gTree on the display list.  For addGrob this
    specifies a descendant of the specified gTree. gPath should
    be treated as a regular expression.  Values are recycled across
    elements of the gPath (e.g., c(TRUE, FALSE) means
    that every odd element of the gPath will be treated as
    a regular expression).
  gPath, or whether all matches
    should be affected.
  addGrob returns a grob object;  grid.add returns NULL.addGrob copies the specified grob and returns a modified
  grob. grid.add destructively modifies a grob on the display list.
  If redraw
  is TRUE it then redraws everything to reflect the change. setChildren is a basic function for setting all children
  of a gTree at once (instead of repeated calls to addGrob).grob, getGrob,
  addGrob, removeGrob.