ggplot mapping fill based on two different conditions

Question

I'd like to make a map where the states are colored according to one criteria, and crosshatched (or somehow otherwise differentiated) according to a different criteria. So far what I have is

library(ggmap)
library(mapdata)
library(ggplot2)
library(dplyr)
region<-c("california","nevada","oregon","washington")
var1<-c(0,1,0,1)
var2<-c(3,4,4,3)
my_data<-data.frame(region, var1, var2)
all_states_map <- map_data("state")
Total <- inner_join(all_states_map,my_data, by = "region")
Total$var1<-as.factor(Total$var1)
my_map <- ggplot() + geom_polygon(data=Total, aes(x=long, y=lat, group = Total$group, fill=Total$var1),colour="white",
                         show.legend=TRUE) + scale_fill_manual(values=c("blue","gray"))

So now my states are color coded based on whether var1 is 0 or 1. Is there a way to overlay something on top of that to crosshatch states where var2 is 3, and leave alone the states where var2 is 4?

Edit: what I'd like is something like this:

You might have to do something like this example: http://stackoverflow.com/questions/21677489/fill-geospatial-polygons-with-pattern-r — Mike H., May 08 '16 at 21:42

Psidom · Answer 1 · 2016-05-08T21:18:03.207

Is this something close to what you'd like to see?

ggplot() + geom_polygon(data=Total, aes(x=long, y=lat, group = group, 
                        fill = paste(var1, var2, sep = ", ")), colour="white") + 
           scale_fill_manual(values=c("blue","gray", "green", "red")) + 
           labs(fill = "(var1, var2)")

Another option is you set the transparency as another dimension of the plot, so it would be like, which might be closer to what you want?

ggplot() + geom_polygon(data=Total, aes(x=long, y=lat, group = group, 
                        fill = var1, alpha = as.factor(var2)), colour="white") + 
           scale_fill_manual(values=c("blue","red")) +
           scale_alpha_manual(values = c(0.5, 1)) + 
           labs(alpha = "var2", fill = "var1")

I might end up needing to do something like that, but it's not exactly what I want. I edited the question with an example. I'm looking for a way to have the two different things look independent. — user5457414, May 08 '16 at 20:55

score 2 · Accepted Answer · answered May 09 '16 at 10:01

This might not be ideal but maybe helps in some way?

library(ggmap)
library(mapdata)
library(ggplot2)
library(dplyr)
library(sp)
region<-c("california","nevada","oregon","washington")
var1<-c(0,1,0,1)
var2<-c(3,4,4,3)
my_data<-data.frame(region, var1, var2)
all_states_map <- map_data("state")
Total <- inner_join(all_states_map,my_data, by = "region")
Total$var1<-as.factor(Total$var1)

randomPoints <- NULL

# For each region find a set of points inside each state
for(i in region){
  sub <- subset(Total, region == i)
  sub.sr = SpatialPolygons(list(Polygons(list(Polygon(sub[,1:2])), "a")))

  smple <- as.data.frame(spsample(sub.sr, n = 100, "regular"))

  temp <- data.frame(x = smple[,1], y = smple[,2], region = i, var1 = unique(sub$var1), var2 = unique(sub$var2))
  randomPoints <- rbind(randomPoints, temp)
}

ggplot() + 
  geom_polygon(data=Total, aes(x=long, y=lat, group = group, fill=var1), color = "white") + 
  geom_point(data = randomPoints, aes(x = x, y = y, shape = as.factor(var2)), size = 1) + 
  scale_shape_manual(values = c(1, 2))

score 1 · Answer 3 · edited May 23 '17 at 12:16

It looks like there is no easy solution to this problem in ggplot. One way of differentiating could be to use different contours around the polylines like in this example:

ggplot() + 
  geom_polygon(data=Total, aes(x=long, y=lat, group = Total$group, 
                              fill=Total$var1,colour=as.factor(var2)),
                              ,size=3,show.legend=TRUE) + 
  scale_fill_manual(values=c("blue","gray"))+
  scale_color_manual(values=c("black",NA))

But as you can see this results in an inconsistent line width between California and the other states because of the polygon plotting order. We can fix this in a quick and dirty way by increasing the groupnumber of the states where var2 equals 3:

Total2<-Total%>%
  mutate(group=ifelse(var2==3,group+100,group))

ggplot() + 
  geom_polygon(data=Total2, aes(x=long, y=lat, group = Total2$group, 
                               fill=Total2$var1,colour=as.factor(Total2$var2)),
               ,size=3,show.legend=TRUE) + 
  scale_fill_manual(values=c("blue","gray"))+
  scale_color_manual(values=c("black",NA))

If you really want to go for the crosshatching you may have to abandon ggplot for this one:

Fill Geospatial polygons with pattern - R

ggplot mapping fill based on two different conditions

3 Answers3