Center facets in ggplot2

Question

I'm plotting geom_smooths in facets grouped by size:

library(ggplot2)
ggplot(df,
       aes(x = pos, y = mean_ratio_f ))+
  geom_smooth(aes(group = factor(size)), method = "lm", se = FALSE, linewidth = 0.5) +
  # facets:
  facet_wrap(. ~ size, scales = 'free_x')+
  labs(x ="X", 
       y = "Y")

Unfortunately the last three facets (for size groups 23, 24,and 25) are aligned to the left margin so that there is a gap to their right (which also creates the impression of the whole plot being tilted to the right!):

It appears to me that the issue can be solved by centering the three facets in question (but maybe there are other solutions as well). How can the factes be rearranged so that the last three facets are centered?

Data:

df <- structure(list(size = c(3L, 3L, 4L, 4L, 5L, 5L, 6L, 6L, 7L, 7L, 
                              8L, 8L, 9L, 9L, 10L, 10L, 11L, 11L, 12L, 12L, 13L, 13L, 14L, 
                              14L, 15L, 15L, 16L, 16L, 17L, 17L, 18L, 18L, 19L, 19L, 20L, 20L, 
                              21L, 21L, 22L, 22L, 23L, 23L, 24L, 24L, 25L, 25L), pos = c(1.5, 
                                                                                         2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 
                                                                                         2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 
                                                                                         2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 2, 1.5, 2), mean_ratio_f = c(527.899043866778, 
                                                                                                                                                              1223.75592041265, 26.7055556681507, 1014.99764633205, 6.47082070497567, 
                                                                                                                                                              863.659744048962, 3.81972089409093, 777.045156006896, 2.46140197567771, 
                                                                                                                                                              745.040410893806, 2.22400421369641, 759.114492391129, 2.13729390098214, 
                                                                                                                                                              687.177457687369, 1.98034033753045, 778.931235189388, 1.90373974226176, 
                                                                                                                                                              718.311850673966, 1.80384197110368, 825.996874022512, 1.81708729221153, 
                                                                                                                                                              784.264857079573, 1.7777262939807, 752.39972151211, 1.76691331278538, 
                                                                                                                                                              860.318640599953, 1.75527539730966, 869.777351603508, 1.74520729149527, 
                                                                                                                                                              880.417441527199, 1.73611317639682, 780.755824759386, 1.78837402005967, 
                                                                                                                                                              868.750440691095, 1.70425949150671, 804.161284483241, 1.70130414461642, 
                                                                                                                                                              827.894751207786, 1.6956455656474, 846.217696086233, 1.6805039077424, 
                                                                                                                                                              796.011388849723, 1.65481637360088, 811.918292989823, 1.67084107927763, 
                                                                                                                                                              920.002748174406), mean_ratio_f_log = c(6773.00321795844, 17499.3396876788, 
                                                                                                                                                                                                      91.9407050566451, 14640.9637434847, 0.961390621510839, 12925.4581530315, 
                                                                                                                                                                                                      0.962105282138507, 11965.2882380283, 0.959588977914962, 11925.034356026, 
                                                                                                                                                                                                      0.95894420256844, 12389.1090131876, 0.962673236418588, 10291.5804363065, 
                                                                                                                                                                                                      0.961229361905838, 13564.6305043359, 0.959542208244426, 11807.7801051298, 
                                                                                                                                                                                                      0.958279155901719, 13222.8288829741, 0.960694717000605, 14050.9037663119, 
                                                                                                                                                                                                      0.959865919899295, 13196.4602878018, 0.960818003520457, 18197.3072369647, 
                                                                                                                                                                                                      0.959524692210418, 16167.0124087112, 0.962044614557777, 19156.2703675997, 
                                                                                                                                                                                                      0.958319770694746, 12192.6024672023, 0.96568915213801, 14355.9254483709, 
                                                                                                                                                                                                      0.957678872168589, 12384.5704259404, 0.956930859337691, 15515.5122785017, 
                                                                                                                                                                                                      0.964217350399733, 14886.2543318109, 0.958708854899801, 12105.1755086371, 
                                                                                                                                                                                                      0.959842413426268, 12265.603237096, 0.954623252993519, 15048.4316206923
                                                                                                                                                              )), class = c("grouped_df", "tbl_df", "tbl", "data.frame"), row.names = c(NA, 
                                                                                                                                                                                                                                        -46L), groups = structure(list(size = 3:25, .rows = structure(list(
                                                                                                                                                                                                                                          1:2, 3:4, 5:6, 7:8, 9:10, 11:12, 13:14, 15:16, 17:18, 19:20, 
                                                                                                                                                                                                                                          21:22, 23:24, 25:26, 27:28, 29:30, 31:32, 33:34, 35:36, 37:38, 
                                                                                                                                                                                                                                          39:40, 41:42, 43:44, 45:46), ptype = integer(0), class = c("vctrs_list_of", 
                                                                                                                                                                                                                                                                                                     "vctrs_vctr", "list"))), row.names = c(NA, -23L), class = c("tbl_df", 
                                                                                                                                                                                                                                                                                                                                                                 "tbl", "data.frame"), .drop = TRUE))

Even if you cut of the last three facets it's look tilted to the right - at least when I look at it. I don't think that it would help to align the last three facets to the center. It is some other kind of optical illusion that makes the diagram tilted. — ChristianL, Jan 10 '23 at 08:14
Interesting question! Not clear if you want to centre the last row or remove the optical illusion. — zx8754, Jan 10 '23 at 08:25
[Relevant](https://stackoverflow.com/questions/51010990/r-ggplot2-setting-the-last-plot-in-the-midle-with-facet-wrap) — Sotos, Jan 10 '23 at 08:45
`ggh4x::facet_manual` is not really working here it seems since the y coordinates of the last row are creating an empty space between the first and second plot of every other row — Maël, Jan 10 '23 at 09:16

teunbrand · Answer 1 · 2023-01-10T18:07:51.683

You can set the layout with ggh4x::facet_manual() and then manually adjust any spacing in the gtable that seem superfluous to you.

library(ggplot2)
library(ggh4x)

# Data omitted from reprex for brevity, but taken from question
# df <- structure(...)

# Create layout
design <- matrix(
  c(1:20, NA, 21:23, NA),
  5, 5, byrow = TRUE
)

# Make plot
p <- ggplot(df, aes(x = pos, y = mean_ratio_f ))+
  geom_smooth(aes(group = factor(size)), 
              method = "lm", se = FALSE, linewidth = 0.5) +
  facet_manual(vars(size), design = design, scales = "free_x") +
  labs(x ="X", y = "Y")

# Convert to gtable
gt <- ggplotGrob(p)
#> `geom_smooth()` using formula = 'y ~ x'

# Set some widths to zero
# I don't know of a programmatic way to get the right indices
gt$widths[8] <- unit(0, "cm")

# Plotting
grid::grid.newpage(); grid::grid.draw(gt)

^{Created on 2023-01-10 with reprex v2.0.2}

Disclaimer: I'm the author of ggh4x

Center facets in ggplot2

1 Answers1