一张ggplot2图上有两个单独的颜色渐变色标

Question

I am trying to plot a map that has two different color scales on it for different countries.

Example of my data:

>df
         country responses         area
1         Canada       150 northamerica
2  United States        70 northamerica
3         Mexico        65 northamerica
4        Germany       120       europe
5         France        55       europe
6          Spain        71       europe

I would like there to be one gradient (blues) showing the number of responses for northamerica and another one (reds) showing the number of responses for europe on the same world map.

I have tried subsetting the data and doing two different geom_map lines but I get Scale for 'fill' is already present. Adding another scale for 'fill', which will replace the existing scale. Scale for 'fill' is already present. Adding another scale for 'fill', which will replace the existing scale.

na <- df[df$area=="northamerica",]
euro <- df[df$area=="europe",]

library(maptools)
library(ggplot2)
data(wrld_simpl)
wrld_simpl@data$id <- wrld_simpl@data$NAME
wrld <- fortify(wrld_simpl, region="id")
wrld <- subset(wrld, id != "Antarctica")

gg <- ggplot()
gg <- gg + geom_map(data=wrld, map=wrld, aes(map_id=id, x=long, y=lat),      fill="white", color="#7f7f7f", size=0.25)
gg <- gg + geom_map(data=na, map=wrld, aes(map_id=country, fill=responses),  color="white", size=0.25)
gg <- gg + scale_fill_continuous(high = "#132B43", low = "#56B1F7", name="Number of\nresponses\nNorth America")
gg <- gg + geom_map(data=euro, map=wrld, aes(map_id=country, fill=responses),  color="white", size=0.25)
gg <- gg + scale_fill_continuous(high = "#67000d", low = "#fcbba1", name="Number of\nresponses\nEurope")
gg <- gg + coord_map()
gg <- gg + labs(x="", y="")
gg <- gg + theme(plot.background = element_rect(fill = "transparent", colour = NA),
             panel.border = element_blank(),
             panel.background = element_rect(fill = "transparent", colour = NA),
             panel.grid = element_blank(),
             axis.text = element_blank(),
             axis.ticks = element_blank(),
             legend.position = "right")
gg

I just get the last color scale coded instead of both:

I can get the two sets of data to be different colors using this code (below) but I can not figure out how to get it to be scaled by the number of responses in this case.

gg <- ggplot()
gg <- gg + geom_map(data=wrld, map=wrld, aes(map_id=id, x=long, y=lat), fill="white", color="#7f7f7f", size=0.25)
gg <- gg + geom_map(data=na, map=wrld, aes(map_id=country, fill=responses),  color="white", size=0.25, fill = "blue")
gg <- gg + geom_map(data=euro, map=wrld, aes(map_id=country, fill=responses),  color="white", size=0.25, fill = "red")
gg <- gg + coord_map()
gg <- gg + labs(x="", y="")
gg <- gg + theme(plot.background = element_rect(fill = "transparent", colour = NA),
             panel.border = element_blank(),
             panel.background = element_rect(fill = "transparent", colour = NA),
             panel.grid = element_blank(),
             axis.text = element_blank(),
             axis.ticks = element_blank(),
             legend.position = "right")
gg

Different colors for the two regions but not scaled by responses

I have tried other variations of code that would take a while to include here and some of them I would be embarrassed to show since I reached a point where I was just trying anything and everything. If anyone has any suggestions that would be wonderful. I would like to avoid making two maps and then putting them on top of each other but if it comes to it I will do that.

Thank you in advance!

Answer 1

I think this will get you close to what you want.

# Other packages needed in order to to run this code
install.packages("rgeos", "mapproj")

ggplot() +
  geom_map(data=wrld, map=wrld, aes(map_id=id, x=long, y=lat),      fill="white", color="#7f7f7f", size=0.25) +
  geom_map(data=df, map=wrld, aes(map_id=country, fill=area, alpha = responses),  color="white", size=0.25) +
  scale_fill_manual(values = c("#132B43", "#67000d")) + 
  scale_alpha_continuous(range = c(0.3, 1)) + 
  coord_map() +
  labs(x="", y="") +
  theme(plot.background = element_rect(fill = "transparent", colour = NA),
    panel.border = element_blank(),
    panel.background = element_rect(fill = "transparent", colour = NA),
    panel.grid = element_blank(),
    axis.text = element_blank(),
    axis.ticks = element_blank(),
    legend.position = "right"

The deepest color of each is constant from what you had, but I'm scaling the colors by changing their transparency instead of the lowest color, so I can't specify the lightest color. I can adjust how transparent it is at the bottom - and you can play with that.