ggplot2 both axis labels inside plot area - r

Question

I would like to create a ggplot2 with both the y-axis and x-axis labels on the inside, i.e., facing inwards and placed inside the plot area.
This previous SO answer by Z.Lin solves it for the case of the y-axis, and I've got that working just fine. But extending that approach to both axes has me stumped. grobs is hard, I think.
So I attempted to start small, by adapting Z.Lin's code to work for the x-axis instead of the y-axis, but I have not been able to achieve even that. grobs is really complicated. My attempt (below) runs without errors/warnings until grid.draw(), where it crashes and burns (I think I'm misusing some args somewhere, but I can't identify which and at this point I'm just guessing).
# locate the grob that corresponds to x-axis labels
x.label.grob <- gp$grobs[[which(gp$layout$name == "axis-b")]]$children$axis
# remove x-axis labels from the plot, & shrink the space occupied by them
gp$grobs[[which(gp$layout$name == "axis-b")]] <- zeroGrob()
gp$widths[gp$layout$l[which(gp$layout$name == "axis-b")]] <- unit(0, "cm")
# create new gtable
new.x.label.grob <- gtable::gtable(widths = unit(1, "npc"))
# place axis ticks in the first row
new.x.label.grob <-
gtable::gtable_add_rows(
new.x.label.grob,
heights = x.label.grob[["heights"]][1])
new.x.label.grob <-
gtable::gtable_add_grob(
new.x.label.grob,
x.label.grob[["grobs"]][[1]],
t = 1, l = 1)
# place axis labels in the second row
new.x.label.grob <-
gtable::gtable_add_rows(
new.x.label.grob,
heights = x.label.grob[["heights"]][2])
new.x.label.grob <-
gtable::gtable_add_grob(
new.x.label.grob,
x.label.grob[["grobs"]][[2]],
t = 1, l = 2)
# add third row that takes up all the remaining space
new.x.label.grob <-
gtable::gtable_add_rows(
new.x.label.grob,
heights = unit(1, "null"))
gp <-
gtable::gtable_add_grob(
x = gp,
grobs = new.x.label.grob,
t = gp$layout$t[which(gp$layout$name == "panel")],
l = gp$layout$l[which(gp$layout$name == "panel")])
grid.draw(gp)
# Error in unit(widths, default.units) :
# 'x' and 'units' must have length > 0
I guess my question can be split into three semi-independent parts, where each subsequent question supersedes the earlier ones (so if you can answer a later question, there will be no need to bother with the earlier ones):
can anyone adapt the existing answer to the x-axis?
can anyone provide code in that vein to get both axes inside?
does anyone know of a neater way to achieve both axes inside for ggplot2?
Here's my MWE (mostly replicating Z.Lin's answer, but with new data):
library(dplyr)
library(magrittr)
library(ggplot2)
library(grid)
library(gtable)
library(errors)
df <- structure(list(
temperature = c(200, 300, 400, 500, 600, 700, 800, 900),
diameter =
structure(
c(13.54317, 10.32521, 10.23137, 17.90464, 29.98183, 55.65514, 101.60747, 147.3074),
id = "<environment>",
errors = c(1.24849, 0.46666, 0.36781, 0.48463, 0.94639, 1.61459, 6.98346, 12.18353),
class = "errors")),
row.names = c(NA, -8L),
class = "data.frame")
p <- ggplot() +
geom_smooth(data = df %>% filter(temperature >= 400),
aes(x = temperature, y = diameter),
method = "lm", formula = "y ~ x",
se = FALSE, fullrange = TRUE) +
# experimental errors as red ribbon (instead of errorbars)
geom_ribbon(data = df,
aes(x = temperature,
ymin = errors_min(diameter),
ymax = errors_max(diameter)),
fill = alpha("red", 0.2),
colour = alpha("red", 0.2)) +
geom_point(data = df,
aes(x = temperature, y = diameter),
size = 0.7) +
geom_line(data = df,
aes(x = temperature, y = diameter),
size = 0.15) +
scale_x_continuous(breaks = seq(200, 900, 200)) +
scale_y_log10(breaks = c(10, seq(30, 150, 30)),
labels = c("10", "30", "60", "90", "120", "150=d/nm")) +
theme(panel.grid.major = element_blank(),
panel.grid.minor = element_blank(),
axis.title.y = element_blank(),
axis.text.y = element_text(hjust = 0))
# convert from ggplot to grob object
gp <- ggplotGrob(p)
y.label.grob <- gp$grobs[[which(gp$layout$name == "axis-l")]]$children$axis
gp$grobs[[which(gp$layout$name == "axis-l")]] <- zeroGrob()
gp$widths[gp$layout$l[which(gp$layout$name == "axis-l")]] <- unit(0, "cm")
new.y.label.grob <- gtable::gtable(heights = unit(1, "npc"))
new.y.label.grob <-
gtable::gtable_add_cols(
new.y.label.grob,
widths = y.label.grob[["widths"]][2])
new.y.label.grob <-
gtable::gtable_add_grob(
new.y.label.grob,
y.label.grob[["grobs"]][[2]],
t = 1, l = 1)
new.y.label.grob <-
gtable::gtable_add_cols(
new.y.label.grob,
widths = y.label.grob[["widths"]][1])
new.y.label.grob <-
gtable::gtable_add_grob(
new.y.label.grob,
y.label.grob[["grobs"]][[1]],
t = 1, l = 2)
new.y.label.grob <-
gtable::gtable_add_cols(
new.y.label.grob,
widths = unit(1, "null"))
gp <-
gtable::gtable_add_grob(
x = gp,
grobs = new.y.label.grob,
t = gp$layout$t[which(gp$layout$name == "panel")],
l = gp$layout$l[which(gp$layout$name == "panel")])
grid.draw(gp)
> sessionInfo()
R version 3.6.2 (2019-12-12)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 18.04.5 LTS
Matrix products: default
BLAS: /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.7.1
LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.7.1
locale:
[1] LC_CTYPE=en_GB.UTF-8 LC_NUMERIC=C
[3] LC_TIME=en_GB.UTF-8 LC_COLLATE=en_GB.UTF-8
[5] LC_MONETARY=en_GB.UTF-8 LC_MESSAGES=en_GB.UTF-8
[7] LC_PAPER=en_GB.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_GB.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] grid stats graphics grDevices utils datasets methods
[8] base
other attached packages:
[1] errors_0.3.4 gtable_0.3.0 ggplot2_3.3.2 magrittr_1.5 dplyr_1.0.2
loaded via a namespace (and not attached):
[1] rstudioapi_0.11 splines_3.6.2 tidyselect_1.1.0 munsell_0.5.0
[5] lattice_0.20-41 colorspace_1.4-1 R6_2.5.0 rlang_0.4.8
[9] tools_3.6.2 nlme_3.1-148 mgcv_1.8-31 withr_2.3.0
[13] ellipsis_0.3.1 digest_0.6.27 yaml_2.2.1 tibble_3.0.4
[17] lifecycle_0.2.0 crayon_1.3.4 Matrix_1.2-18 purrr_0.3.4
[21] farver_2.0.3 vctrs_0.3.4 glue_1.4.2 compiler_3.6.2
[25] pillar_1.4.6 generics_0.1.0 scales_1.1.1 pkgconfig_2.0.3

Answer 1

Rather than "freezing" the plot as a grob tree then hacking the grobs, I thought it might be useful to see how we could move the axes inside but keep the object as a ggplot. The way to do this is to write a function that takes your plot, extracts the necessary information, then builds axes and adds them as annotations.
The returned object is a normal ggplot, to which you can add layers, scales and modify themes as normal:
move_axes_inside <- function(p)
{
b <- ggplot_build(p)
x_breaks <- b$layout$panel_scales_x[[1]]$break_info()
y_breaks <- b$layout$panel_scales_y[[1]]$break_info()
x_range <- b$layout$panel_params[[1]]$x.range
y_range <- b$layout$panel_params[[1]]$y.range
y_breaks$major <- diff(y_breaks$range)/diff(y_range) * y_breaks$major +
(y_breaks$range[1] - y_range[1])/diff(y_range)
x_breaks$major <- diff(x_breaks$range)/diff(x_range) * x_breaks$major +
(x_breaks$range[1] - x_range[1])/diff(x_range)
y <- grid::yaxisGrob(at = y_breaks$major, label = y_breaks$labels, main = FALSE)
x <- grid::xaxisGrob(at = x_breaks$major, label = x_breaks$labels, main = FALSE)
p + annotation_custom(y, xmin = x_range[1], xmax = x_range[1]) +
annotation_custom(x, ymin = y_range[1], ymax = y_range[1]) +
theme(axis.text.y = element_blank(),
axis.ticks = element_blank(),
axis.text.x = element_blank())
}
So testing it with your plot we get:
p2 <- move_axes_inside(p)
p2
And we can change theme elements etc:
p2 + theme(panel.grid.major = element_line())
This would need a bit of development and testing to get it working with discrete axes and so on, but it should work for arbitrary continuous axes as-is.

Answer 2

In case anyone else happens to be looking for a way to make a compact plot using ggplot2, for example for placement inside a page margin, I perhaps you'll be helped by the full code for a fairly publication-ready inside-the-margin plot made possible by Allan Cameron's elegant approach in the answer above.
Placing a plot inside a page margin is usually not advisable, and depends on the available margin, the type of document, etc. In any case, it's probably smart to make the plot as clutter-free and stream-lined as possible. That's why, in my case, I was looking for a way to keep as much of the plot inside the panel's footprint, so to speak.
Enough background, here's the code:
library(dplyr)
library(magrittr)
library(ggplot2)
library(grid)
library(gtable)
library(errors)
theme_set(theme_grey())
move_axes_inside <- function(p) {
b <- ggplot_build(p)
x_breaks <- b$layout$panel_scales_x[[1]]$break_info()
y_breaks <- b$layout$panel_scales_y[[1]]$break_info()
x_range <- b$layout$panel_params[[1]]$x.range
y_range <- b$layout$panel_params[[1]]$y.range
y_breaks$major <-
diff(y_breaks$range) / diff(y_range) * y_breaks$major +
(y_breaks$range[1] - y_range[1]) / diff(y_range)
x_breaks$major <-
diff(x_breaks$range) / diff(x_range) * x_breaks$major +
(x_breaks$range[1] - x_range[1]) / diff(x_range)
y <-
grid::yaxisGrob(
at = y_breaks$major,
label = y_breaks$labels,
gp =
gpar(
lwd = 1, # line width of axis and tick marks
fontsize = 8,
cex = 0.8, # multiplier to font size
lineheight = 0.8), # tick mark length
main = FALSE)
x <-
grid::xaxisGrob(
at = x_breaks$major,
label = x_breaks$labels,
gp =
gpar(
lwd = 2, # draw axis with thicker line width
fontsize = 8,
cex = 0.8, # multiplier to font size
lineheight = 0.8), # tick mark length
main = FALSE)
p <-
p +
annotation_custom(
# draw y-axis, shifted slightly inwards (so that axis is inside panel.border)
grob = y,
xmin = x_range[1] + 0.01 * diff(x_range),
xmax = x_range[1] + 0.01 * diff(x_range)) +
annotation_custom(
grob = x,
ymin = y_range[1] + 0.01 * diff(y_range),
ymax = y_range[1] + 0.01 * diff(y_range)) +
theme(
axis.ticks = element_blank(),
axis.title.y = element_blank(),
axis.text.y = element_blank(),
axis.text.x = element_blank())
return(p)
}
p <- ggplot() +
geom_line(
stat = "smooth", method = lm, formula = "y ~ x",
se = FALSE, fullrange = TRUE,
data = df %>% filter(temperature >= 400),
aes(x = temperature, y = diameter),
colour = "blue", size = 2, alpha = 0.35) +
# experimental errors as red ribbon (instead of errorbars)
geom_ribbon(
data = df,
aes(x = temperature,
ymin = errors_min(diameter),
ymax = errors_max(diameter)),
fill = alpha("red", 0.25),
colour = NA) +
# data points excluded in linear fit
geom_point(
data = df %>% filter(temperature < 400),
aes(x = temperature, y = diameter),
# by default, shape=19 (filled circle)
# https://blog.albertkuo.me/post/point-shape-options-in-ggplot/
# I'd like a solid circle, so shape 16 it is
size = 1.2, shape = 16, colour = alpha("red", 0.25)) +
# data points included in linear fit
geom_point(
data = df %>% filter(temperature >= 400),
aes(x = temperature, y = diameter),
size = 1.2, shape = 16, colour = alpha("red", 0.45)) +
# I ended up putting the x-axis unit label on the outside because
# however I tried, it would not fit inside and I was not able to
# rotate the x-axis labels on the inside.
labs(x = "$T_\\mathrm{a}/\\si{\\celsius}$") +
scale_x_continuous(
breaks = seq(200, 900, 100),
# first element can't be empty string - if so then all labels dont print (weird bug?)
labels = c(" ", " ", "400", " ", "600", " ", "800", " ")) +
scale_y_log10(
breaks = c(10, 50, 90, 130),
labels = c("\\num{10}", "\\num{50}", "\\num{90}", "$\\num{130}=d/\\si{\\nm}$")) +
# note that we set some theme settings inside the move_axes_inside() function
theme(
# l = -1 was required to completely fill the space with plot panel
# b = 0 because we are making room for x-axis title on the outside
plot.margin = margin(t = 0, r = 0, b = 0, l = -1, "mm"),
# smaller text size in x-axis title, trying to conform with fontsize inside axis
# vjust moves the title closer to the x-axis line, value optimised optically
axis.title.x = element_text(size = 8 * 0.8, vjust = 2.0),
# grid lines just look busy in such a small plot
panel.grid.major = element_blank(),
panel.grid.minor = element_blank())
move_axes_inside(p)
Here's a screen-shot of the result, in a document compiled with knitr and LaTeX and with the plot inside \marginpar{}: