CODEWITHSUNDEEP
rggplot2
Sal
Sal

Reputation: 117

Color coded world map with ggplot2 and geom_map

I am trying to plot a world map where the color of each country depends on the value of a variable in the dataframe.

> affiliation
# A tibble: 252 × 2
                 region value
                  <chr> <dbl>
1                 Aruba     0
2           Afghanistan     0
3                Angola     0
4              Anguilla     0
5               Albania     0
6               Finland     1
7               Andorra     0
8  United Arab Emirates     0
9             Argentina     2
10              Armenia     0
# ... with 242 more rows

The code I have works fine: 

library(ggplot2)
library(ggthemes)

ggplot(affiliation, aes(map_id = region)) + 
    geom_map(aes(fill = value), map = worldMap, color='grey', size=0.3) + 
    expand_limits(x = worldMap$long, y = worldMap$lat) +
    theme_few()+
    theme(legend.position = "bottom",
         axis.ticks = element_blank(), 
         axis.title = element_blank(), 
         axis.text =  element_blank()) +
    scale_fill_gradient(low="white", high="darkblue", name="Number of Affiliates") +
    guides(fill = guide_colorbar(barwidth = 10, barheight = .5))

My problem is that most of the values are 0, 1 or 2, very few values in the 20-30 but 1 outlier country has a value in the 330. This makes the color scale useless because that country is shown saturated in color whereas all the countries with much lower values appear white.

I tried to replace geom_map(aes(fill = value),… with geom_map(aes(fill = log(value)),… but in this case the scale in the legend shows 0 to 5+ (instead of 0 to 330).

What can I do to better control the color saturation of the many countries that have low values in order to make them more visible on the world map ? Thank you

Upvotes: 0

Views: 1958

Answers (2)

Nathan Werth
Nathan Werth

Reputation: 5263

Most of the continuous scale functions in ggplot2 accept a trans argument, which specifies the transformation to use on that aesthetic. This will automatically handle the transformation and labelling.

In your example, adding trans = "log1p" (not just "log" because your data has a couple 0 values) to the arguments to scale_gradient_n could help.

Upvotes: 2

jdobres
jdobres

Reputation: 11957

Instead of scale_fill_gradient, why not try a call to scale_fill_gradientn, setting color stops as needed. For example:

scale_fill_gradientn(colours = c('#ff0000', '#cccccc', '#0000ff'), values = c(0, 30, 331))

Upvotes: 2

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