Adding an addition to an existing legend

[Maso]

Hi!

I have created a map in R displaying the population growth for different counties in Norway. Is there any way I can add a box at the end to display the mean value for Norway (see picture below)?

This is my current code:

andel_over_67 <- ggplot(map1, aes(long, lat, group = group)) +
geom_polygon(aes(fill = prosent), color = "black", size = 0.10) +
scale_fill_manual(values = mycolors, labels=c("Oslo (14,6%)", "Rogaland (18,8%)", "Viken (20,3%)", "Trøndelag (20,4%)", "Vestland (20,5%)", "Agder (20,9%)", "Troms og Finnmark (22,0%)", "Møre og Romsdal (22,9%)", "Vestfold og Telemark (23,7%)", "Nordland (24,6%)", "Innlandet (25,3%)")+
theme_classic()+
theme(legend.position = "bottom",
axis.title.x = element_blank(),
axis.text.x = element_blank(),
axis.ticks.x = element_blank(),
axis.title.y = element_blank(),
axis.text.y = element_blank(),
axis.ticks.y = element_blank(),
axis.line.y = element_blank(),
axis.line.x = element_blank(),
legend.title = element_blank(),
legend.key.size = unit(0.5, "cm"),
legend.text = element_text(size=12),
text = element_text( family = "sans")
)
andel_over_67

Thanks!

[scottyd22]

One way would be to add the mean value for Norway to the values (mycolors in your case) and labels vectors within scale_fill_manual. Without the map1 data, I could not recreate your specific situation. Below is an example using the mtcars dataset with comments noting the new addition.

library(tidyverse)

df = mtcars %>%
  mutate(cyl = as.character(cyl)) %>%
  count(cyl)

df
#>   cyl  n
#> 1   4 11
#> 2   6  7
#> 3   8 14

ggplot(df, aes(x = cyl, y = n)) +
  geom_bar(stat = 'identity', aes(fill = cyl)) +
  scale_fill_manual(values = c('4' = 'red', 
                               '6' = 'blue', 
                               '8' = 'orange', 
                               'NA' = 'black' # added to values
                               ),
                    labels = c('4 (5%)', 
                               '6 (10%', 
                               '8 (20%)', 
                               'New Item' # added to labels
                               )
                    )

Created on 2022-11-02 with reprex v2.0.2.9000

[Maso]

Thank you so much for the quick reply. Im using a color palette that only has 9 colors. In my case, "mycolors" refers to this code:

nb.cols <- 11
mycolors <- colorRampPalette(brewer.pal(9, "Reds"))(nb.cols)

Does that change anything? Is it still possible to add to the values, or do I have to manually assign a color to each observation?

Thanks again!

[scottyd22]

You could try adding another line to the code you just shared, which adds white as the last color:
mycolors <- c(mycolors, '#FFFFFF')

Then, add the desired corresponding label at the end of labels vector within your plot:
labels=c("Oslo (14,6%)", ..., "Norge XX%").