theme_bw() strips all color off my ggplot

Question

library(tidyverse)
ggplot(mtcars, aes(cyl, mpg)) + 
  geom_point() + 
  theme_bw() + 
  geom_hline(aes(yintercept = 20), color = "red")

This code above is the nice black and white theme, with a red horizontal line. The code below also is supposed to be the black and white theme, this time with a red vertical line. But the plot lacks any color at all. Why is theme_bw() stripping out all color from my plot below?

library(tidyverse)
library(lubridate)

df <- 
  tibble(
    date = as.Date(41000:42000, origin = "1899-12-30"), 
    value = c(rnorm(500, 5), rnorm(501, 10))
  ) %>% 
  mutate(year = as.factor(year(date)))

ggplot(df, aes(date, value)) + 
  geom_line() + 
  geom_vline(
    xintercept = as.numeric(df$date[yday(df$date) == 1]), color = "red"
  ) + 
  scale_x_date(
    date_labels = "%b", breaks = scales::pretty_breaks(), expand = c(0, 0)
  ) +
  facet_grid(.~ year, space = 'free_x', scales = 'free_x', switch = 'x') +
  labs(x = "") +
  theme_bw(base_size = 14, base_family = 'mono') +
  theme(panel.grid.minor.x = element_blank()) + 
  theme(panel.spacing.x = unit(0, "line")) +
  theme(strip.placement = 'outside', strip.background.x = element_blank())

You just need to increase size of line (`geom_vline(size = 2, ...)`), all this happens because you split plot into facets and there edges cover the line (or remove facets). — pogibas, Oct 02 '18 at 13:19
@PoGibas thanks that works! but how do I eliminate the facet black lines? What ends up happening now is I get the `size=2` red line, with a `size=1` black line drawn on top of it. Looks like a racing stripe (which I don't want in this case) — stackinator, Oct 02 '18 at 13:24
Here's a [related question](https://stackoverflow.com/questions/46220242/ggplot2-outside-panel-border-when-using-facet), where the answer uses `theme_classic()` and adds lines on top and right. — aosmith, Oct 02 '18 at 16:04

Maurits Evers · Accepted Answer · 2018-10-02T13:59:39.980

You could remove the facet panel borders with panel.border = element_blank() inside theme

ggplot(df, aes(date, value)) +
  geom_line() +
  geom_vline(
    xintercept = as.numeric(df$date[yday(df$date) == 1]), color = "red") +
  scale_x_date(
    date_labels = "%b", breaks = scales::pretty_breaks(), expand = c(0, 0)) +
  facet_grid(.~ year, space = 'free_x', scales = 'free_x', switch = 'x') +
  labs(x = "") +
  theme_bw(base_size = 14, base_family = 'mono') +
  theme(
      panel.grid.minor.x = element_blank(),
      panel.spacing.x = unit(0, "line"),
      panel.border = element_blank(),
      strip.placement = 'outside',
      strip.background.x = element_blank())

Update

To use facets and have the red lines not overlap the facet borders here is bit of a "hacky" solution:

First, draw without panel borders

gg <- ggplot(df, aes(date, value)) +
      geom_line() +
      geom_vline(
        xintercept = as.numeric(df$date[yday(df$date) == 1]), color = "red") +
      scale_x_date(
        date_labels = "%b", breaks = scales::pretty_breaks(), expand = c(0, 0)) +
      facet_grid(.~ year, space = 'free_x', scales = 'free_x', switch = 'x') +
      labs(x = "") +
      theme_bw(base_size = 14, base_family = 'mono') +
      theme(
          panel.grid.minor.x = element_blank(),
          panel.spacing.x = unit(0, "line"),
          panel.border = element_blank(),
          strip.placement = 'outside',
          strip.background.x = element_blank())

Then we extract the y-axis range for the panel, and add a geom_rect to manually draw the panel border

ylim <- ggplot_build(gg)$layout$panel_params[[1]]$y.range
gg <- gg +
    geom_rect(
        xmin = min(df$date), xmax = max(df$date),
        ymin = ylim[1], ymax = ylim[2],
        fill = NA, colour = "black")

It's a bit hacky because you need to break up the plotting into two steps in order to be able to extract the y-axis range for the panel.

Thank you, I thought about that too, but I really need the border. It is useful so I'll upvote it. — stackinator, Oct 02 '18 at 13:33
@stackinator No problem. I think you're stuck with having to make a compromise here. Either remove the panel borders, or remove the facets (as PoGibas suggested), or increase the size of the lines to draw on top of the black borders. — Maurits Evers, Oct 02 '18 at 13:35
I may be missing something but I am unable to draw on top of the black borders. I am only able to draw under them. It seems, no matter where you place the `geom_vline()` in the code, the facet borders always get drawn last, thus being on top of all other lines that ggplot draws. — stackinator, Oct 02 '18 at 13:40
@stackinator Yes, the red `geom_vline` will always be drawn first . I've added a somewhat "hacky" solution that should do what you're after. Please take a look. — Maurits Evers, Oct 02 '18 at 14:00
and that solves it. Thank you. I usually give things 24 hours before marking as solved. To see what the most elegant solution is. I'll do that tomorrow, and it'll likely be this I imagine. — stackinator, Oct 02 '18 at 14:06
@stackinator Great, glad it was helpful. Curious to see alternatives too. — Maurits Evers, Oct 02 '18 at 14:21

Z.Lin · Answer 2 · 2018-10-03T12:12:15.597

Another hack, if you are willing to dig into the grobs:

gp <- ggplotGrob(p) # where p is the original ggplot object

# for each panel grob, change the order of grobs such that the grob corresponding
# to geom_vline (should have a name like "GRID.segments.XXXX") lies above the grob
# corresponding to the facet outline (should have a name like "panel.border..rect.XXXX")
for(i in grep("panel", gp$layout$name)){
  old.order <- gp$grobs[[i]]$childrenOrder
  new.order <- c(old.order[-grep("segments", old.order)],
                 old.order[grep("segments", old.order)])
  gp$grobs[[i]]$childrenOrder <- new.order
}

grid::grid.draw(gp)

theme_bw() strips all color off my ggplot

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