Using a custom gradient fill based on two different columns-CodePudding

I am trying to have two different fill colors for each US state based on two different columns of my dataset. For this, I am using the counties and coloring half of them which are below the state centroid based on Qt column and another half based on Apo.

This is my data:

read.table(text = "State     Apo    Qt
NJ  1     10
MO  2     20
SD  3     30
NY  4     40
FL  5     50
OK  6     60
NE  7     70
KY  8     80
ME  9     90
CA  10  100
NC  11  110
MA  12  120
CT  13  140", header = T, stringsAsFactor = F) -> ex1

Here I am getting the US maps (with and without counties). Then, I join the county map with my dataset based on comparing the centroid of each county to its corresponding state (to decided whether to join Apo or Qt).

library(tidyverse)
library(usmap)
library(RColorBrewer)

#preparing data for join
ex1 %>% 
  pivot_longer(-State) -> ex_1_long

# geo dataset of US states map and US counties map
us <- usmap::us_map()
usc <- usmap::us_map(regions = "counties")

## creating a polygon dataframe with counties and values from my dataset
## (lower half of the state gets Apo and upper half gets Qt)
usc %>% 
  # getting counties centroid
  group_by(full, county) %>% 
  mutate(county.y.center =  mean(range(y))) %>% 
  # getting states centroid
  group_by(full) %>% 
  mutate(state.y.center =  mean(range(y))) %>% 
  # deciding whether to have Apo or Qt by comparing State and County centroids
  mutate(var = ifelse(state.y.center > county.y.center, "Apo", "Qt")) %>% 
  left_join(ex_1_long, ., by = c("State" = "abbr", "name" = "var")) %>% 
  pivot_wider(names_from = "name", values_from = "value") -> usc_map_ex

Then, I use usc_map_ex for plotting and deciding the fill colors.

## a color pallete
## I want the lower half (Apo) to have a shade of blue and upper half to be in Greens
mcolor <- c(colorRampPalette(brewer.pal(3, "Greens"))(3), 
            colorRampPalette(brewer.pal(3, "Blues"))(3))

## plot
ggplot()   
  # polygon for Qt
  geom_polygon(data = {usc_map_ex %>% filter(is.na(Apo))},
               aes(x,y, group = group, fill = (Qt), color = ""))  
  # polygon for Apo (multiplyong by three to have a different range of values than Qt)
  geom_polygon(data = {usc_map_ex %>% filter(is.na(Qt))},
               aes(x,y, group = group, fill = (Apo)*3, color = ""))   
  # adding the outline of each state
  geom_polygon(data = us,
               aes(x,y, group = group), fill = NA, color = "black")   
  # removing the outline of counties
  scale_colour_manual(values = 'transparent', guide = "none")   
  # custom fill gradient to have different shades of colors for each variable
  scale_fill_gradientn(name = "test",
                       breaks = c(0,5,15, 20, 270, 540),
                       labels = c(0,5,15, 7, 90, 180),
                       values = c(0,5,15, 20, 270, 540) / 540,
                       #limits = c(0, 540),
                       colors = mcolor,
                       guide = guide_colorbar(barwidth = 0.8, barheight = 18), 
                       trans = "log")  
  
  theme_void()

^{Created on 2022-09-13 by the}

CodePudding user response：

You can use fill option accordingly instead of using scale_fill_gradient if you just want to assign each half of the state with one color.

ggplot()  
 # polygon for Qt
geom_polygon(data = {usc_map_ex %>% filter(is.na(Apo))},
             aes(x,y, group = group),fill='steelblue')  
# polygon for Apo
geom_polygon(data = {usc_map_ex %>% filter(is.na(Qt))},
             aes(x,y, group = group),fill='darkseagreen3')  
# adding the outline of each state
geom_polygon(data = us,
             aes(x,y, group = group), fill = NA, color = "black")   
# removing the outline of counties
scale_colour_manual(values = 'transparent',guide="none")  
theme_void()