alignment of gtables

gtables_align.r

library(gtable)

gcore <- gtable_matrix(name="core",
                       grobs=matrix(list(rectGrob(gp=gpar(fill="blue",alpha=0.5))),1,1),
                       widths=unit(5,"cm"), heights=unit(3,"cm"))

gtop <- gtable_matrix(name="top",
                       grobs=matrix(list(rectGrob(gp=gpar(fill="red",alpha=0.5))),1,1),
                       widths=unit(5,"cm"), heights=unit(1,"cm"))

gleft <- gtable_matrix(name="left",
                       grobs=matrix(list(rectGrob(gp=gpar(fill="green",alpha=0.5))),1,1),
                       widths=unit(1,"cm"), heights=unit(3,"cm"))

align_table <- function(core, top, left, just=c("center", "center")){

  gl <- grid.layout(nrow=2,ncol=2,
                    widths=unit.c(sum(left$widths), sum(core$widths)),
                    heights=unit.c(sum(top$heights), sum(core$heights)),
                    just=just)
  g1 <- gtable_gTree(core, vp=viewport(layout.pos.row=2, layout.pos.col=2))
  g2 <- gtable_gTree(top, vp=viewport(layout.pos.row=1, layout.pos.col=2))
  g3 <- gtable_gTree(left, vp=viewport(layout.pos.row=2, layout.pos.col=1))
  
  gTree(children=gList(g1,g2,g3), vp=viewport(layout=gl))
}

grid.newpage()
g <- align_table(gcore,gtop,gleft)
grid.draw(g)