ggplot2 - custom grob over axis lines

Question

I\'m trying to generate an axis line break in ggplot2 (with a white segment over the axis lines) and I\'m having some trouble.

Using the informative post annotate-gg

Answer 1

You were close. The layout data frame is were you turned off clipping. There is another column in the layout data frame that gives the order in which the various plot elements are drawn - z. The plot panel (including the annotation) is drawn second (after the background), then later the axes are drawn. Change the value of z for the plot panel to something larger than the z values for the axes.

library(ggplot2) # devtools::install_github("hadley/ggplot2")
library(grid)
library(scales)


data("economics_long")
econ <- economics_long
econ$value01 <- (econ$value01/2)


x <- ggplot(econ, aes(date, value01,group=1)) + scale_y_continuous(labels=c(0.0,0.1,0.2,0.3,0.4,0.5,1.0), breaks=c(0.0,0.1,0.2,0.3,0.4,0.5,0.6),limits = c(0,.6),expand = c(0, 0)) +
  geom_smooth(colour="deepskyblue", show.legend = TRUE ) + theme_bw()

theme_white <- theme(panel.background=element_blank(),
                     panel.border=element_rect(color="transparent"),
                     plot.margin = unit(c(.2, 0, .2, .2), "cm"),
                     panel.grid.major.y=element_blank(),
                     panel.grid.major.x=element_blank(),
                     panel.grid.minor.x=element_blank(),
                     panel.grid.minor.y=element_blank(),
                     axis.title.y = element_blank(),
                     axis.line.x=element_line(color="gray", size=1),
                     axis.line.y=element_line(color="gray", size=1),
                     axis.text.x=element_text(size=12),
                     axis.text.y=element_text(size=12),
                     axis.ticks=element_line(color="gray", size=1),
                     legend.position="none"
)
x <- x + theme_white


gline = linesGrob(y = c(0, 1.5),x = c(-.015, .015),  gp = gpar(col = "black", lwd = 2.5)) 
gline2 = linesGrob(y = c(-0.25, 0.5),x = c(0, 0),  gp = gpar(col = "red", lwd = 5))

p = x + annotation_custom(gline, ymin=.55, ymax=.575, xmin=-Inf, xmax=Inf) + 
  annotation_custom(gline, ymin=.525, ymax=.55, xmin=-Inf, xmax=Inf) +
  annotation_custom(gline2, ymin=.55, ymax=.575, xmin=-Inf, xmax=Inf)

# grobs are placed under the axis lines....

g = ggplotGrob(p)
g$layout$clip[g$layout$name=="panel"] <- "off"

g$layout  # Note that z for panel is 1.  Change it to something bigger.

g$layout$z[g$layout$name=="panel"] = 17    

grid.newpage()
grid.draw(g)