How to use geom_bar and use two categorical variables on the x axis-CodePudding

I try to do a bar plot, with an X axis a bit different than usual. The idea is to represent this axis by the initial variable (code) and by a grouping variable (region). Each code has one region attributed to it. And I would like vertical line to delimitate my regions on the plot.

Here is a reprex

library(dplyr)
library(ggplot2)
data <- tibble::tribble(
                           ~code,    ~term,          ~estimate,           ~std.error,       ~statistic,             ~p.value,      ~region,
                          "ANTA", "t_chla", 0.0577051712200805, 0.000720537559840254, 80.0862778518777, 1.51491004165028e-36,      "Polar",
                          "ARCH", "t_chla", 0.0528096415790542,  0.00237431411186973, 22.2420619559337, 9.38778083531695e-08, "Equatorial",
                          "ARCT", "t_chla", 0.0381489725623347, 0.000549351930679462, 69.4435942277484,  7.1661522966813e-84,      "Polar",
                          "BPLR", "t_chla", 0.0334314725309052, 0.000908084662707285, 36.8153696498248,   6.728272457306e-26,      "Polar",
                          "EMED", "t_chla",  0.048713647973686,  0.00179735526256328, 27.1029601038437, 1.37127584382531e-20,  "Temperate",
                          "SANT", "t_chla", 0.0311278181792805, 0.000594175450783383, 52.3882602996143, 4.93281235468381e-67,      "Polar",
                          "SPSG", "t_chla", 0.0676467149977894,  0.00461643829029263,  14.653442923744, 1.64755108560374e-06, "Equatorial",
                          "WMED", "t_chla", 0.0359293074812375, 0.000954627809780489, 37.6369796826883, 1.88418982949485e-42,  "Temperate"
                          )

data$code <- factor(data$code, levels = c("ANTA", "SANT", "ARCT", "BPLR", "EMED", "WMED", "SPSG", "ARCH"))


ggplot(data) 
  geom_bar(aes(y = estimate, x = code, fill = code), stat = "identity") 
  geom_errorbar(aes(ymin = estimate - std.error, ymax = estimate   std.error, x = code)) 
  scale_fill_brewer(palette = "Set1", guide = "none") 
  theme_bw() 
  ylab("Specifc absorption") 
  xlab("Oceanic province") 
  ggtitle("Specific absorption")

So the idea is to have a vertical line between BPLR and EMED and between WMED and SPSG, with the bar grouped under the label Polar, Temperate and Equatorial.

Thanks in advance for your answers.

CodePudding user response：

What about adding facet_wrap and panel.spacing = unit(0, 'lines') to your plot?

ggplot(data) 
  geom_bar(aes(y = estimate, x = code, fill = code), stat = "identity") 
  geom_errorbar(aes(ymin = estimate - std.error, ymax = estimate   std.error, x = code)) 
  scale_fill_brewer(palette = "Set1", guide = "none") 
  theme_bw() 
  ylab("Specifc absorption") 
  xlab("Oceanic province") 
  ggtitle("Specific absorption")  
  facet_wrap(~region, scales = 'free_x')  
  theme(panel.spacing = unit(0, 'lines'))

Edit: updated to manually add vertical line and labels

Here is another option for adding the grouping to the bars. Lots of customization can be done with text size, position, color, font, etc.

ggplot(data) 
  geom_bar(aes(y = estimate, x = code, fill = code), stat = "identity") 
  geom_errorbar(aes(ymin = estimate - std.error, ymax = estimate   std.error, x = code)) 
  scale_fill_brewer(palette = "Set1", guide = "none") 
  theme_bw() 
  ylab("Specifc absorption") 
  xlab("Oceanic province") 
  ggtitle("Specific absorption")  
  geom_vline(xintercept = c(4.5, 6.5))  
  annotate(geom = 'text', x = 2.5, y = .07, label = 'Polar')  
  annotate(geom = 'text', x = 5.5, y = .07, label = 'Temperate')  
  annotate(geom = 'text', x = 8, y = .07, label = 'Equitorial')