How to align caption text with left bar in a bar chart? - r

Question

I am trying to align the caption text in a bar chart, so that it will start at the same vertical margin as the left bar.
library(ggplot2)
library(tibble)
my_df <-
tibble::tribble(~response, ~estimate,
"little_bit", 0.353477,
"no", 0.307639,
"very", 0.338883)
ggplot(my_df, aes(x = reorder(response, -estimate), y = estimate)) +
geom_bar(stat = "identity", width = 0.9, fill = "royalblue") +
ggtitle("do you like swimming with fish?") +
ylab("") +
labs(caption = "this is my caption") +
theme_minimal() +
theme(
axis.line.x = element_blank(),
axis.line.y = element_blank(),
axis.text.y = element_blank(),
panel.grid = element_blank(),
panel.grid.major=element_blank(),
plot.title = element_text(hjust = 0.5, size = 26),
axis.text.x = element_text(angle = 0, size = 14, margin = margin(t = 0, r = 20, b = 0, l = 0)),
axis.title.x = element_blank(),
legend.title = element_blank(),
plot.caption = element_text(hjust = 0, size = 8),
plot.caption.position = "plot") ## <-- I thought this would help, but no...
Is there a way to align the caption such as the following?

Answer 1

To get your desired result set the caption position to "panel" and remove the expansion of the x-scale:
library(ggplot2)
library(tibble)
my_df <-
tibble::tribble(~response, ~estimate,
"little_bit", 0.353477,
"no", 0.307639,
"very", 0.338883)
ggplot(my_df, aes(x = reorder(response, -estimate), y = estimate)) +
geom_bar(stat = "identity", width = 0.9, fill = "royalblue") +
ggtitle("do you like swimming with fish?") +
scale_x_discrete(expand = c(0, 0)) +
labs(caption = "this is my caption", y = NULL) +
theme_minimal() +
theme(
axis.line.x = element_blank(),
axis.line.y = element_blank(),
axis.text.y = element_blank(),
panel.grid = element_blank(),
panel.grid.major=element_blank(),
plot.title = element_text(hjust = 0.5, size = 26),
axis.text.x = element_text(angle = 0, size = 14, margin = margin(t = 0, r = 20, b = 0, l = 0)),
axis.title.x = element_blank(),
legend.title = element_blank(),
plot.caption = element_text(hjust = 0, size = 8),
plot.caption.position = "panel")

Answer 2

Or, a very common workaround for those cases would be to annotate outside of the plot area. (I am using annotate(geom = "text",...) - you could also use geom_text, but you would only need a data frame for it.)
I personally prefer the annotate option as it is more versatile and generalisable for other purposes as well.
library(ggplot2)
my_df <-
tibble::tribble( ~response, ~estimate, "little_bit", 0.353477, "no", 0.307639, "very", 0.338883)
barwidth <- 0.9
ggplot(my_df, aes(x = reorder(response, -estimate), y = estimate)) +
geom_bar(stat = "identity", width = barwidth, fill = "royalblue") +
annotate(
geom = "text",
x = 1 - barwidth / 2, hjust = 0, # that's the trick
y = -0.1, # play around with y. you could also set it relativ to your bar heights
label = "this is my caption"
) +
coord_cartesian(clip = "off", ylim = c(0, NA)) + # necessary to set axis limits and clip off to annotate beyond
ggtitle("do you like swimming with fish?") +
theme_minimal() +
theme(plot.margin = margin(b = 1, unit = "inch")) # margin randomly chosen. unfortunately also necessary