Epistemic_and_Ethical_Value_Tradeoffs/ggplot_dual_axis.R at master · scrim-network/Epistemic_and_Ethical_Value_Tradeoffs · GitHub

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ggplot_dual_axis = function(plot1, plot2, which.axis = "x") {

  require(gtable)

  grid.newpage()

  # Increase right margin if which.axis == "y"
  if(which.axis == "y") plot1 = plot1 + theme(plot.margin = unit(c(0.7, 1.5, 0.4, 0.4), "cm"))

  # Extract gtable
  g1 = ggplot_gtable(ggplot_build(plot1))

  g2 = ggplot_gtable(ggplot_build(plot2))

  # Overlap the panel of the second plot on that of the first
  pp = c(subset(g1$layout, name == "panel", se = t:r))

  g = gtable_add_grob(g1, g2$grobs[[which(g2$layout$name == "panel")]], pp$t, pp$l, pp$b, pp$l)

  # Steal axis from second plot and modify
  axis.lab = ifelse(which.axis == "x", "axis-b", "axis-l")

  ia = which(g2$layout$name == axis.lab)

  ga = g2$grobs[[ia]]

  ax = ga$children[[2]]

  # Switch position of ticks and labels
  if(which.axis == "x") ax$heights = rev(ax$heights) else ax$widths = rev(ax$widths)

  ax$grobs = rev(ax$grobs)

  if(which.axis == "x")

    ax$grobs[[2]]$y = ax$grobs[[2]]$y - unit(1, "npc") + unit(0.15, "cm") else

      ax$grobs[[1]]$x = ax$grobs[[1]]$x - unit(1, "npc") + unit(0.15, "cm")

  # Modify existing row to be tall enough for axis
  if(which.axis == "x") g$heights[[2]] = g$heights[g2$layout[ia,]$t]

  # Add new row or column for axis label
  if(which.axis == "x") {

    g = gtable_add_grob(g, ax, 2, 4, 2, 4)

    g = gtable_add_rows(g, 2*g2$heights[1], 1)

    g = gtable_add_grob(g, g2$grob[[6]], 2, 4, 2, 4)

  } else {

    g = gtable_add_cols(g, g2$widths[g2$layout[ia, ]$l], length(g$widths) - 1)

    g = gtable_add_grob(g, ax, pp$t, length(g$widths) - 1, pp$b)

    g = gtable_add_grob(g, g2$grob[[7]], pp$t, length(g$widths), pp$b - 1)

  }


  return(g)

  # draw it with grid.draw(g)

}