Labeling a US States map - r

Question

I made a map in R and was wondering how to label the States Codes (variable which is in my dataset) appropriately. Using the simple geom_text or even geom_text_repel I get a lot of labels for each State (I can actually understand why), as I proceed to show:
Map
How can I solve it so each State gets 1 and only 1 text abbreviation (these State Codes are in my dataset as a variable under the name State Codes)? Thanks in advance.
Code below:
library(tidyverse)
library(maps)
library(wesanderson)
library(hrbrthemes)
ggplot(data = data,
mapping = aes(x = long,
y = lat,
group = group,
fill = black_percentage)) +
geom_polygon(col = "black") +
geom_text(aes(label = black_percentage)) +
theme_void() +
theme(legend.position = "bottom",
legend.title = element_blank(),
plot.title = element_text(hjust = 0.5, family = "Times", face = "bold"),
plot.subtitle = element_text(hjust = 0.5, family = "Times", face = "italic"),
plot.caption = element_text(family = "Times", face = "italic"),
legend.key.height = unit(0.85, "cm"),
legend.key.width = unit(0.85, "cm")) +
scale_fill_gradient(low = "#E6A0C4",
high = "#7294D4") +
labs(title = "Percentage of Black People, US States 2018",
subtitle = "Pink colors represent lower percentages. Light-blue colors represents higer percentages") +
ggsave("failed_map.png")

Answer 1

Can you provide the/some sample data?
One possible reason for multiple labels is that each state has multiple rows in the data, so ggplot thinks it needs to plot multiple labels. If you only need a single label, a solution is to create a separate summary dataset, which has only one row for each state/label. You then provide this summary data to geom_text() rather than the original data. Although not the problem in this instance, this is a solution to the common problem of 'blurry' labels; when 10's or 100's of labels are printed on top of one another they appear blurry, but when a single label is printed it appears fine.
Looking at your code and mapping aesthetics, it looks like geom_text() is inheriting the x and y aesthetics from the first ggplot() line. Therefore geom_text() will make a label for every value of x and y (long and lat) per state. This also explains why the labels all appear to follow the state borders.
I would suggest that you summarise each state to a single (x, y) coordinate (e.g. the middle of the state), and give this to geom_text(). Again, without some sample data it may be hard to explain, but something like:
# make the summary label dataframe
state_labels <- your_data %>%
group_by(state) %>%
summarise(
long = mean(long),
lat = mean(lat),
mean_black = mean(black_percentage)
)
# then we plot it
ggplot(data = data,
mapping = aes(x = long,
y = lat,
group = group,
fill = black_percentage)) +
geom_polygon(col = "black") +
geom_text(data = state_labels, aes(label = mean_black))
As the name of the x and y coords are the same in your data and the new state_labels summary we made (long and lat), geom_text() will 'inherit' (assume/use) the same x and y aesthetics that you supplied inside the first line of ggplot(). This is convenient, but sometimes can cause you grief if either dataset has different/the same column names or you want to assign different aesthetics. For example, you don't need geom_text() to inherit the fill = black_percentage aesthetic (although in this instance I don't think it will cause a problem, as geom_text() doesn't accept a fill aesthetic). To disable aesthetic inheritance, simply provide inherit.aes = FALSE to the geom. In this instance, it would look like this, note how we now provide geom_text() with x and y aesthetics.
ggplot(data = data,
mapping = aes(x = long,
y = lat,
group = group,
fill = black_percentage)) +
geom_polygon(col = "black") +
geom_text(data = state_labels, aes(x = long, y = lat, label = mean_black), inherit.aes = FALSE)
EDIT If you want a single label, but the label is not a numeric value and you can't calculate a summary statistic using mean or similar, then the same principles apply; you want to create a summarised version of the data, with a single coordinates for each state and a single label - 1 row for each state. There's many ways to do this, but my go-to would be something like dplyr::first or similar.
# make the summary label dataframe
state_labels <- your_data %>%
group_by(state) %>%
summarise(
long = mean(long),
lat = mean(lat),
my_label = first(`State Codes`)
)
# then we plot it
ggplot(data = data,
mapping = aes(x = long,
y = lat,
group = group,
fill = black_percentage)) +
geom_polygon(col = "black") +
geom_text(data = state_labels, aes(label = my_label))
Finally, ggplot has several built-in functions to plot and map spatial data. It is a good idea to use these where possible, as it will make your life a lot easier. A great 3-part tutorial can be found here, and it even includes an example of exactly what you are trying to do.