ggplot: placing facet strips above axis title

Question

I want to create a plot where the axis titles are on the top/left and the axis labels on the bottom/right. This can be done by creating a duplicate axis and removing the axis titles and labels on those sides where they are not needed (by the theming options).

I am encountering however a problem when it comes to placing the x-axis title on the top in a facetted plot. For some reason the strip text of the facets is below the axis title, despite using the option strip.placement="outside". Interestingly, if I don't hide the axis lables (see graph below), they are below the strip text, but the axis title is above the strip text.

Any idea how to move the axis title also below the strip.text? Note that I am using ggplot ggplot2_3.3.0.9000. Many thanks.

library(tidyverse)

iris %>% 
  ggplot()+
  geom_bar(aes(x=Sepal.Length,
               y=Sepal.Width),
           stat="identity")+
  facet_wrap(~Species,
             strip.position = "top")+
  scale_y_continuous(sec.axis = dup_axis())+  #create secondary axis
  scale_x_continuous(sec.axis = dup_axis())+  #create secondary 
  theme(strip.placement = "outside",
        axis.title.x.top = element_text(hjust=0),  #left align axis title on top
        axis.title.x.bottom = element_blank(), #remove title on x axis/bottom
        axis.ticks.length.x.top = unit(0, units="cm"), #remove axis ticks on top
        axis.text.y.left = element_blank(), #remove axis label on left side
        axis.title.y.right = element_blank(), #remove axis title on right side
        axis.ticks.length.y.left = unit(0, units="cm")) #remove axis ticks on left


sessionInfo()
#> R version 3.6.1 (2019-07-05)
#> Platform: x86_64-w64-mingw32/x64 (64-bit)
#> Running under: Windows 10 x64 (build 18362)
#> 
#> Matrix products: default
#> 
#> locale:
#> [1] LC_COLLATE=English_Austria.1252  LC_CTYPE=English_Austria.1252   
#> [3] LC_MONETARY=English_Austria.1252 LC_NUMERIC=C                    
#> [5] LC_TIME=English_Austria.1252    
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> other attached packages:
#> [1] forcats_0.4.0      stringr_1.4.0      dplyr_0.8.3        purrr_0.3.3       
#> [5] readr_1.3.1        tidyr_1.0.2        tibble_2.1.3       ggplot2_3.3.0.9000
#> [9] tidyverse_1.3.0   
#> 
#> loaded via a namespace (and not attached):
#>  [1] tidyselect_0.2.5 xfun_0.12        haven_2.2.0      lattice_0.20-38 
#>  [5] colorspace_1.4-1 vctrs_0.2.2      generics_0.0.2   htmltools_0.4.0 
#>  [9] yaml_2.2.0       rlang_0.4.3      pillar_1.4.3     glue_1.3.1      
#> [13] withr_2.1.2      DBI_1.1.0        dbplyr_1.4.2     modelr_0.1.5    
#> [17] readxl_1.3.1     lifecycle_0.1.0  munsell_0.5.0    gtable_0.3.0    
#> [21] cellranger_1.1.0 rvest_0.3.5      evaluate_0.14    labeling_0.3    
#> [25] knitr_1.27       fansi_0.4.1      highr_0.8        broom_0.5.3     
#> [29] Rcpp_1.0.3       scales_1.1.0     backports_1.1.5  jsonlite_1.6    
#> [33] farver_2.0.3     fs_1.3.1         hms_0.5.3        digest_0.6.23   
#> [37] stringi_1.4.5    grid_3.6.1       cli_2.0.1        tools_3.6.1     
#> [41] magrittr_1.5     crayon_1.3.4     pkgconfig_2.0.3  xml2_1.2.2      
#> [45] reprex_0.3.0     lubridate_1.7.4  assertthat_0.2.1 rmarkdown_2.1   
#> [49] httr_1.4.1       R6_2.4.1         nlme_3.1-140     compiler_3.6.1

^{Created on 2020-02-06 by the reprex package (v0.3.0)}

tjebo tjebo · Accepted Answer · 2020-02-06T11:50:36

This behaviour is generally desired. This becomes particularly clear when removing theme(strip.placement = 'outside'). I personally feel that it is visually much clearer this way.

I also feel that you are possibly looking for a plot title (you could use labs(title = 'Sepal.Length') rather than x axis title.

For your question, I guess one cannot get around messing with the grobs. Here one quick hack to simply swap the rows in the gtable layout:

library(tidyverse)
library(gtable)
library(grid)

p <- 
  ggplot(iris)+
    geom_bar(aes(x=Sepal.Length, y=Sepal.Width), stat="identity")+
    facet_wrap(~Species, strip.position = "top") +
    scale_x_continuous(sec.axis = dup_axis()) +
    theme(strip.placement = "outside")

gp <- ggplotGrob(p)

# gp$layout #helps you to understand the gtable object 
# gtable_show_layout(ggplotGrob(p)) #helps you to understand the gtable object 

t_title <- gp$layout[gp$layout[['name']] == 'xlab-t' ,][['t']]
t_strip <- gp$layout[grepl('strip', gp$layout[['name']]),][['t']]

gp$layout[gp$layout[['name']] == 'xlab-t' ,][['t']] <- unique(t_strip)
gp$layout[gp$layout[['name']] == 'xlab-t' ,][['b']] <- unique(t_strip)
gp$layout[grepl('strip', gp$layout[['name']]),][['t']] <- t_title
gp$layout[grepl('strip', gp$layout[['name']]),][['b']] <- t_title

grid.newpage()
grid.draw(gp)

^{Created on 2020-02-06 by the reprex package (v0.3.0)}

ggplot: placing facet strips above axis title

1 Answers