How to use a continuous color scale for thematic maps in the R package tmap?

Question

When I make a choropleth with tmap where a continuous variable is mapped to fill color, tmap discretizes the variable and plots color by category. For example, this code

library(tmap)
data(World)
tm_shape(World) + tm_polygons(col="gdp_cap_est")

produces a map where countries are colored based on whether their GDP per capita is in the range $0-20,000, $20,000-40,000, etc. I would like a map where GDP/capita is mapped continuously to colors or shades of color, so that small differences in GDP entail small differences in color on the map. Does tmap have this capability?

Answer 1

We can use style = cont or order .

library(tmap)
data(World)

# Map the value to a continuous gradient
tm_shape(World) + 
  tm_polygons(col = "gdp_cap_est",
              style = "cont")

# Map the order to a continuous gradient
tm_shape(World) + 
  tm_polygons(col = "gdp_cap_est",
              style = "order")