After lurking around for some time, this is my first question here - I'm an absolute novice so please forgive any lack of knowledge about this forum's customs and technical details of R.

I want to plot a map of Germany, in which the fill of the federal states reflects the inhabitants' preferences, like I have done here:

My data looks as follows:

I want to plot the map like this:

#loading libraries
    library(ggplot2)
    library(raster)

#retrieving map
germany <- getData(country = "Germany", level = 1)

#drawing map as plot
ggplot()  
geom_polygon(data = germany,
             aes(x = long, y = lat, group = group))

Which provides me with this .

My question now is: how can I integrate the data from the table above as a gradient fill for the different federal states?

And: is it possible to show the percentages in the plot in the respective federal state instead of having a gradient legend next to the plot?

Thanks a lot for any advice, it is much appreciated!

CodePudding user response：

This should provide a starter, using simple features (package sf) and joining sausage data to the Bundesland data.
I've created the Sausages data, assuming the percentages are numeric values, if your data is as set out in the table (i.e. as "12,5%" strings) there will be a bit of work to convert these (generally it is much better to add data to a question in a reproducible manner ie using the output of dput(your_data) or as a data frame, i.e. dat <- data.frame(your_variables...) ).
Apologies for using the point decimal notation.

library(ggplot2)
library(raster)
library(dplyr)
library(sf)

dat <- structure(list(Bundesland = c("Baden-Württemberg", "Bayern", 
                                     "Berlin", "Brandenburg", "Bremen", "Hamburg", "Hessen", "Mecklenburg-Vorpommern", 
                                     "Niedersachsen", "Nordrhein-Westfalen", "Rheinland-Pfalz", "Saarland", 
                                     "Sachsen", "Sachsen-Anhalt", "Schleswig-Holstein", "Thüringen"
), Sausage = c(0.287, 0.317, 0.2, 0.208, 0.192, 0.206, 0.244, 
               0.248, 0.265, 0.266, 0.289, 0.273, 0.225, 0.25, 0.266, 0.241)), class = "data.frame", row.names = c(NA, 
                                                                                                                   -16L))


germany <- 
  getData(country = "Germany", level = 1) %>% 
  st_as_sf() %>% 
  left_join(dat, by = c("NAME_1" = "Bundesland"))

ggplot(germany)  
  geom_sf(aes(fill = Sausage)) 
  geom_sf_text(aes(label = scales::percent(Sausage))) 
  scale_fill_gradient(low = "yellow", high = "red") 
  theme(legend.position = "none")

^{Created on 2022-02-20 by the}