ggplot2 overlay of barplot and line plot

This does most of what you want: inward pointing tick marks, combined legends from two plots, overlapping of two plots, and moving the y-axis of one to the right side of the plot.

library(ggplot2) # version 2.2.1 library(gtable) # version 0.2.0 library(grid) # Your data df1 <- data.frame(frax = c(16,30,60,64), solvb = c(0,0,100,100)) df2 <- data.frame(type = factor(c("mascot","mstat"), levels = c("mascot","mstat")), frax = c(30,35,40,45,50,55), phos = c(542,413,233,500,600,650)) # Base plots p1 <- ggplot(df2, aes(x = frax, y = phos, fill = type)) + geom_bar(stat = "identity", position = "dodge") + scale_x_continuous("fractions", expand = c(0,0), limits = c(16, 64), breaks = seq(20,60,5), labels = seq(20, 60, 5)) + scale_y_continuous("Phospho hits", breaks = seq(0,1400,250), expand = c(0,0), limits = c(0, 700)) + scale_fill_discrete("") + theme_bw() + theme(panel.grid = element_blank(), legend.key = element_rect(colour = "white"), axis.ticks.length = unit(-1, "mm"), #tick marks inside the panel axis.text.x = element_text(margin = margin(t = 7, b = 0)), # Adjust the text margins axis.text.y = element_text(margin = margin(l = 0, r = 7))) p2 <- ggplot(df1, aes(x = frax, y = solvb)) + geom_line(aes(linetype = "LC Gradient"), colour = "blue", size = .75) + scale_x_continuous("fractions", expand = c(0,0), limits = c(16, 64)) + scale_y_continuous("% Solvent B") + scale_linetype_manual("", values="longdash") + theme_bw() + theme(panel.background = element_rect(fill = "transparent"), panel.grid = element_blank(), axis.ticks.length = unit(-1, "mm"), axis.text.x = element_text(margin = margin(t = 7, b = 0)), axis.text.y = element_text(margin = margin(l = 0, r = 7)), legend.key.width = unit(1.5, "cm"), # Widen the key legend.key = element_rect(colour = "white")) # Extract gtables g1 <- ggplotGrob(p1) g2 <- ggplotGrob(p2) # Get their legends leg1 = g1$grobs[[which(g1$layout$name == "guide-box")]] leg2 = g2$grobs[[which(g2$layout$name == "guide-box")]] # Join them into one legend leg = cbind(leg1, leg2, size = "first") # leg to be positioned later # Drop the legends from the two gtables pos = subset(g1$layout, grepl("guide-box", name), l) g1 = g1[, -pos$l] g2 = g2[, -pos$l] ## Code taken from http://stackoverflow.com/questions/36754891/ggplot2-adding-secondary-y-axis-on-top-of-a-plot/36759348#36759348 # to move y axis to right hand side # Get the location of the plot panel in g1. # These are used later when transformed elements of g2 are put back into g1 pp <- c(subset(g1$layout, name == "panel", se = t:r)) # Overlap panel for second plot on that of the first plot g1 <- gtable_add_grob(g1, g2$grobs[[which(g2$layout$name == "panel")]], pp$t, pp$l, pp$b, pp$l) # ggplot contains many labels that are themselves complex grob; # usually a text grob surrounded by margins. # When moving the grobs from, say, the left to the right of a plot, # Make sure the margins and the justifications are swapped around. # The function below does the swapping. # Taken from the cowplot package: # https://github.com/wilkelab/cowplot/blob/master/R/switch_axis.R hinvert_title_grob <- function(grob){ # Swap the widths widths <- grob$widths grob$widths[1] <- widths[3] grob$widths[3] <- widths[1] grob$vp[[1]]$layout$widths[1] <- widths[3] grob$vp[[1]]$layout$widths[3] <- widths[1] # Fix the justification grob$children[[1]]$hjust <- 1 - grob$children[[1]]$hjust grob$children[[1]]$vjust <- 1 - grob$children[[1]]$vjust grob$children[[1]]$x <- unit(1, "npc") - grob$children[[1]]$x grob } # Get the y axis title from g2 index <- which(g2$layout$name == "ylab-l") # Which grob contains the y axis title? ylab <- g2$grobs[[index]] # Extract that grob ylab <- hinvert_title_grob(ylab) # Swap margins and fix justifications # Put the transformed label on the right side of g1 g1 <- gtable_add_cols(g1, g2$widths[g2$layout[index, ]$l], pp$r) g1 <- gtable_add_grob(g1, ylab, pp$t, pp$r + 1, pp$b, pp$r + 1, clip = "off", name = "ylab-r") # Get the y axis from g2 (axis line, tick marks, and tick mark labels) index <- which(g2$layout$name == "axis-l") # Which grob yaxis <- g2$grobs[[index]] # Extract the grob # yaxis is a complex of grobs containing the axis line, the tick marks, and the tick mark labels. # The relevant grobs are contained in axis$children: # axis$children[[1]] contains the axis line; # axis$children[[2]] contains the tick marks and tick mark labels. # First, move the axis line to the left yaxis$children[[1]]$x <- unit.c(unit(0, "npc"), unit(0, "npc")) # Second, swap tick marks and tick mark labels ticks <- yaxis$children[[2]] ticks$widths <- rev(ticks$widths) ticks$grobs <- rev(ticks$grobs) # Third, move the tick marks ticks$grobs[[1]]$x <- ticks$grobs[[1]]$x - unit(1, "npc") + unit(-1, "mm") # Fourth, swap margins and fix justifications for the tick mark labels ticks$grobs[[2]] <- hinvert_title_grob(ticks$grobs[[2]]) # Fifth, put ticks back into yaxis yaxis$children[[2]] <- ticks # Put the transformed yaxis on the right side of g1 g1 <- gtable_add_cols(g1, g2$widths[g2$layout[index, ]$l], pp$r) g1 <- gtable_add_grob(g1, yaxis, pp$t, pp$r + 1, pp$b, pp$r + 1, clip = "off", name = "axis-r") # Draw it grid.newpage() grid.draw(g1) # Add the legend in a viewport vp = viewport(x = 0.3, y = 0.92, height = .2, width = .2) pushViewport(vp) grid.draw(leg) upViewport() g = grid.grab() grid.newpage() grid.draw(g)