R ggplot 2 legend border issue

Question

I know this is minor, but it's for a publication and will drive me crazy. The bottom of the P0688 box is like 1-2 pixels thinner than the rest. I don't want to make the borders thicker because then it doesn't match the rest of the bar chart.

  plot<- ggplot(tukey_letters, aes(x = variable, y = value.x, 
        fill = L1)) + 
      theme(panel.background=element_rect(fill="#ffffff", color 
      ="#000000"), panel.grid.major=element_blank(), 
    panel.grid.minor=element_blank()) +
      geom_bar(stat = "identity", position=position_dodge(),color="black")+ scale_fill_manual(values=c("#FFFFFF", "#999999"))+ guides(fill=guide_legend(title="Genotype", title.position = "left")) +
  geom_errorbar(aes(ymin=value.x-se, ymax=value.x+se), width=.1,size=.5,position=position_dodge(0.9), color="black")+
  theme(
    axis.title = element_text(size =12, face="bold"),
    axis.text = element_text(angle=30, vjust=0.5,hjust=0.6,size=8,face="bold", color="#000000"),
    axis.ticks = element_line(size = rel(1)),
    axis.ticks.length = unit(0.3, "cm"),
    legend.position = c(0.2, 0.9)
  )+
  labs(
    x="Treatment",
    y="ARI1"
  )+
  #facet_wrap(~L1)+ ## You can use face_wrap function only if you need it+
  geom_text(data =tukey_letters,
            aes(x=xpos, y=ymax+offset_asterisk,label=groups), 
           size = 4,position=position_dodge(0.9) , vjust=-0.5
 )

Bottom of P0688 box

It's not even that noticeable at a smaller size. Still bothers me.

Thanks in advance. Let me know if there is anything else needed to help solve this.

[You may want to check out this question](https://stackoverflow.com/questions/11366964/is-there-a-way-to-change-the-spacing-between-legend-items-in-ggplot2). Look for u/Tung's answer (currently the one at the top). Looks like for vertically-positioned fill legends (like you have), there is still kind of an issue with small spacing differences (it bugs me too - totally get it). Refer to to [this issue](https://github.com/tidyverse/ggplot2/issues/2844) for some additional info. — chemdork123, Apr 03 '20 at 18:29
Yeah, I saw that. Maybe I was implementing something incorrectly because legend.spacing.y was not changing the distance between the white and grey boxes. — Paul Manley, Apr 03 '20 at 19:57
Yeah - I fiddled with it a good 10 min before I found the post and the specific case where vertical legends with fill are kinda bugged. :/ Can you switch to horizontal? :) — chemdork123, Apr 03 '20 at 20:01

tjebo · Answer 1 · 2020-04-04T07:10:14.170

This is due to the filling behaviour of the legend keys. It's a known issue, see this GitHub thread https://github.com/tidyverse/ggplot2/issues/2844. There is also a fix suggested on this site, let me show this here.

library(tidyverse)

ggplot(mtcars) +
  aes(fill=factor(cyl), x=cyl) +
  geom_bar(color = 'black') +
  guides(fill=guide_legend(title.position = "left")) +
  theme(legend.key = element_rect(color="white") +
        legend.position = c(0.2, 0.7))

Enlarged, the legend will look now like this:

Now let's do the fix.

  draw_key_polygon3 <- function(data, params, size) {
  lwd <- min(data$size, min(size) / 4)

  grid::rectGrob(
    width = grid::unit(0.7, "npc"),
    height = grid::unit(0.7, "npc"),
    gp = grid::gpar(
      col = data$colour,
      fill = alpha(data$fill, data$alpha),
      lty = data$linetype,
      lwd = lwd * .pt,
      linejoin = "mitre"
    ))
}

GeomBar$draw_key = draw_key_polygon3

ggplot(mtcars) +
  aes(fill=factor(cyl), x=cyl) +
  geom_bar(color = 'black') +
  guides(fill=guide_legend(title.position = "left")) +
  theme(legend.key = element_rect(color="white", fill = 'white'),
        legend.position = c(0.2, 0.7))

But what is actually going on here? Let's see!

ggplot(mtcars) +
  aes(fill=factor(cyl), x=cyl) +
  geom_bar(color = 'black') +
  guides(fill=guide_legend(title.position = "left")) +
  theme(legend.position = c(0.2, 0.7),
        legend.key = element_rect(color="black", fill = 'white'))

The legend has two borders! One for the legend glyph, the other for the key. You draw the border for the key with the call to theme, and the border around the glyph is created with your color argument in geom_bar

^{Created on 2020-04-04 by the reprex package (v0.3.0)}

R ggplot 2 legend border issue

1 Answers1