Specifying the Colour Scale for Maps in Ggplot

two scale colors in maps ggplot

Solution 1

Accomplish the requirements

By @Allan Cameron .

This issue is solved by ggnewscale, this question has been addressed previously in lot of threads at stack-overflow previously and were solved in alternative ways.

By importing the library ggnewscale with the function new_scale_fill() a new scale color can be applied in an easy way.

library(ggnewscale)

df %>% 
  ggplot(aes(x=long, y= lat, group = group)) +
  geom_polygon(aes_string(fill= "ratio_quan"), size = 0.2)+
  scale_fill_gradient(low ="yellow", high ="blue", na.value="white")+
  new_scale_fill() +
  geom_polygon(aes_string(fill= "ratio_qua"), size = 0.2)+
  scale_fill_gradient(low ="pink", high ="red", na.value="blank")

Solution 2

Alternative

This classic approach is by using to arranged plots with grid.arrange which is less fancy but could be more interpretable.

  p1 <- df %>% 
  ggplot(aes(x=long, y= lat, group = group)) +
  geom_polygon(aes_string(fill= "ratio_quan"), size = 0.2)+
  scale_fill_gradient(low ="yellow", high ="blue", na.value="white")
  p2 <- df %>% 
  ggplot(aes(x=long, y= lat, group = group)) +
  geom_polygon(aes_string(fill= "ratio_qua"), size = 0.2)+
  scale_fill_gradient(low ="yellow", high ="blue", na.value="white")
  grid.arrange(p1, p2, nrow = 1)

As a result two plots with isolated scales are used on the same plots.

Set continuous colour scale in ggplot2

Obviously we don't have your data, but using a simple random example should show the options here.

df <- data.frame(x = rnorm(10000), y = rnorm(10000), z = runif(10000))

Firstly, you could try scale_color_distiller with palette = "Spectral"

ggplot(df, aes(x, y, color = z)) +
  geom_point() +
  scale_color_distiller(palette = 'Spectral')

Another option is to specify a full palette yourself using scale_color_gradientn which allows for arbitrary gradients. This one is a reasonable match for the scale in your example image.

ggplot(df, aes(x, y, color = z)) +
  geom_point() +
  scale_color_gradientn(colours = c('#5749a0', '#0f7ab0', '#00bbb1',
                                    '#bef0b0', '#fdf4af', '#f9b64b',
                                    '#ec840e', '#ca443d', '#a51a49'))

Changing maps colours in ggplot

Here you have two option:

library(RColorBrewer)
library(ggplot2)
library(dplyr)

# get number of groups
groups <- some.eu.maps %>% 
  pull(region) %>% 
  unique() %>% 
  length()

# continuous color scale from red over green to orange
colors1 <- colorRampPalette(c("red", "green", "orange"))(groups) 
# discrete colour scale with red, grren, and orange
colors2 <- rep(c("red", "green", "orange"), length.out = groups)

g <- ggplot(some.eu.maps, aes(x = long, y = lat)) +
  geom_polygon(aes( group = group, fill = region), 
               colour = "black", size = 1.2) 

g + 
  scale_fill_manual(values = colors1)
g + 
  scale_fill_manual(values = colors2)

ggplot map fill with gradient color

You could do a log transform with trans = log:

library(ggplot2)
library(viridis)
#> Loading required package: viridisLite
nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)
nc$value_pop <- c(sample(1:30, nrow(nc)-6, replace = TRUE), 66, 120, 150, 200, 330, 350)
my_breaks <- c(1, 3, 10, 32, 100, 316, 1000)
ggplot(nc, aes(fill = value_pop)) +
    geom_sf()+
    scale_fill_gradientn(colours=rev(magma(6)),
                         name="Susirgimai\n/100.000 gyventojų",
                         na.value = "grey100", 
                         trans = "log",
                         breaks = my_breaks, labels = my_breaks)

^{Created on 2020-03-17 by the reprex package (v0.3.0)}

How to specify bin colors for plot_usmap?

One way would be to manually bin the percentiles and then use the factor levels for your manual breaks and labels.

I've never used this high level function from usmap, so I don't know how to deal with this warning which comes up. Would personally prefer and recommend to use ggplot + geom_polygon or friends for more control.

library(usmap)
library(ggplot2)

fips <- seq(45001,45091,2)
value <- rnorm(length(fips),3000,10000)
mydat <- base::data.frame(fips,value)
mydat$value[mydat$value<0]=0

mydat$perc_cuts <- as.integer(cut(ecdf(mydat$value)(mydat$value), seq(0,1,.25)))

plot_usmap(regions='counties',
           data=mydat,
           values="perc_cuts",include="SC") +
  scale_fill_stepsn(breaks= 1:4, limits = c(0,4), labels = seq(.25, 1, .25),
                    colors=c("blue","green","yellow","red"),
                    guide = guide_colorsteps(even.steps = FALSE))
#> Warning: Use of `map_df$x` is discouraged. Use `x` instead.
#> Warning: Use of `map_df$y` is discouraged. Use `y` instead.
#> Warning: Use of `map_df$group` is discouraged. Use `group` instead.

^{Created on 2020-06-27 by the reprex package (v0.3.0)}

How to create a color palette and export it for use in ggplot2 scale_fill_disteller

When I need to use a custom palette, I either make the palette one-off because it is a few colors that I know I want, or a custom palette function, or the nifty coloRampPalette, which "fills in" colors if you provide some that you want in the palette. If you want to just select values from a sequential palette, you can select [1:n] of that palette, all using scale_*_manual.

 library(ggplot2)

# palette function (hue palette, s is the starting hue)
hue_pal <- function(n,s=15) {
  hues = seq(s, s+360, length = n + 1)
  hcl(h = hues, l = 65, c = 100)[1:n]
}

# ramped palette starting with custom colors
jet_colors <- colorRampPalette(c("#00007F", "blue", "#007FFF", "cyan", "#7FFF7F", "yellow", "#FF7F00", "red", "#7F0000"))

# pre-made palette
cbPalette <- c("#999999", "#E69F00", "#56B4E9", "#009E73", "#F0E442", "#0072B2", "#D55E00", "#CC79A7")

df <- data.frame(x=runif(10),y=runif(10),what = rep(letters[1:5],each=2))
num_colors <- length(unique(df$what))

ggplot(df, aes(x=x,y=y,color=what))+
  geom_point(size=5)+
  scale_color_manual(values = hue_pal(n=num_colors, s=0))
    
ggplot(df, aes(x=x,y=y,color=what))+
  geom_point(size=5)+
  scale_color_manual(values = jet_colors(num_colors))

ggplot(df, aes(x=x,y=y,color=what))+
  geom_point(size=5)+
  scale_color_manual(values = cbPalette[1:num_colors])

How to rescale color mapping in scale_color_distiller (ggplot2)?

rescale the rank to the range of your original df$col.

library(tidyverse)
set.seed(1)
df <- data.frame(x = rnorm(10000), y = rnorm(10000))
df %>%
  mutate(
    col = x + y + x * y,
    scaled_rank = scales::rescale(rank(col), range(col))
  ) %>%
  ggplot(aes(x, y, col = scaled_rank)) +
  geom_point(size = 2) +
  scale_color_distiller(palette = "Spectral")

^{Created on 2021-11-17 by the reprex package (v2.0.1)}

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