How to show legend in a plot with both bars and points?

I have a dataframe the looks as follows:

  COUNTRY YEAR   y
     AT 2019    25
     AT 2020    38.0
     AT 2021    23.4
     BE 2019    11.1
     BE 2020    18.6
     BE 2021    15.0
     DK 2019    31.1
     DK 2020    43.6
     DK 2021    42.0

I am plotting it using both bars (year = 2021) and dots (year = 2015, 2019). I have some issues in getting the legend properly showing the right symbols. I indeed get the following graph

This is the final version of the code I am using:

countries <- c("AT", "BE", "DK")
years <- c(2019, 2020, 2021)
values <- c(25, 38.0, 23.4, 11.1, 18.6, 15.0, 31.1, 43.6, 42.0)

df <- data.frame(
  COUNTRY  = rep(countries, each = 3),
  YEAR = rep(years, times = 3),
  y = values
)
ggplot(df, aes(x = COUNTRY, y = y, group = YEAR, shape = as.factor(YEAR))) +
      geom_bar(data = subset(df, YEAR == 2021), aes(fill = "2021"), stat = 'identity', position = 'dodge', alpha = 0.7) +
      geom_point(data = subset(df, YEAR == 2020), aes(fill = "2020"), position = position_dodge(width = 0.4), size = 3, shape = 19, color = "red") +
      geom_point(data = subset(df, YEAR == 2019), aes(fill = "2019"), position = position_dodge(width = 0.4), size = 3, shape = 4, color = "blue") +
      scale_fill_manual(values = c("2021" = "grey", "2020" = "red", "2019" = "blue")) +
      labs(x = "Country", y = "y", fill = "") +
      theme_minimal() +
      theme(legend.position = "right")

I would like the legend to just show a "bar"/filled box for YEAR = 2021, and the two different shapes for the years 2020 and 2019 respectively.

Solution

Here is one option to achieve your desired result which properly maps on aesthetics instead of setting colors and shapes as arguments in geom_point and takes care that all three legends (fill, color and shape) get merged. Finally I use the override.aes argument of guide_legend to remove the fill colors for the points in the legend.

library(ggplot2)

ggplot(df, aes(x = COUNTRY, y = y, group = YEAR, shape = factor(YEAR))) +
  geom_col(
    data = subset(df, YEAR == 2021), aes(fill = factor(YEAR)),
    position = "dodge", alpha = 0.7
  ) +
  geom_point(
    data = subset(df, YEAR %in% 2019:2020),
    aes(color = factor(YEAR)),
    position = position_dodge(width = 0.4), size = 3
  ) +
  scale_fill_manual(
    values = c("2021" = "grey", "2020" = "red", "2019" = "blue"),
    aesthetics = c("color", "fill")
  ) +
  scale_shape_manual(
    values = c("2020" = 19, "2019" = 4, "2021" = NA),
  ) +
  labs(x = "Country", y = "y", fill = NULL, color = NULL, shape = NULL) +
  theme_minimal() +
  theme(legend.position = "right") +
  guides(
    fill = guide_legend(override.aes = list(fill = c(NA, NA, "grey")))
  )