Reputation: 235
I have a dataset (latitude,longitude,value) over S. California which I am able to plot using the ggplot (see below). Latitude ranges from 31.5 to 35.5 and longitude from -121 to -113. The ggplot map looks fine but I would like to add the state and county border lines to my map.
I have tried adding geom_polygon() but I keep getting the borders for the whole southwest USA instead of over my plot area only (S. California).
I was wondering if anyone would have any suggestions/ideas on how to do this. Thank you very much.
"df is a 3D dataframe (Lat,Lon,value) over S. California" "lat ranges from 31 to 35" "lon ranges from -121 to -113" "value ranges from 3000 to 5000"
library(maps)
library(fields)
library(ggplot2)
state_map <- map_data("state")
bmap=map_data("state", xlim=c(-121,-113), ylim=c(31.5,35.5))
p1 = ggplot() + geom_raster(data = df, aes(x=Lon, y = Lat, fill=Value)) +
coord_fixed(ratio = 1) +
geom_polygon(data=bmap,aes(x=long,y=lat,group=group), inherit.aes=F,
colour='black', fill=NA) +
scale_fill_gradientn(na.value="white",limits = c(3500,5000),
colours=c("yellow","orange","green","blue")) +
theme(panel.background = element_rect(fill = 'white',color="black"),
legend.key = element_blank())
print(p1)
I am getting borders for the entire southwest but I'd like then only for my data area:
Upvotes: 4
Views: 2021
Reputation: 24272
You can zoom the map using coord_cartesian
:
library(maps)
library(fields)
library(ggplot2)
state_map <- map_data("state")
bmap=map_data("state", xlim=c(-121,-113), ylim=c(31.5,35.5))
# Create the df dataset with random numbers for Values
n <- 80
df <- expand.grid(seq(31,35,length.out=n),
seq(-121,-113,length.out=n))
df$Vaule <- 3000+2000*runif(nrow(df))
names(df) <- c("Lat","Lon","Value")
p1 = ggplot() +
coord_fixed(ratio = 1) +
geom_raster(data = df, aes(x=Lon, y = Lat, fill=Value), alpha=0.2) +
geom_polygon(data=bmap,aes(x=long,y=lat,group=group), inherit.aes=F,
colour='black', fill=NA, lwd=1) +
scale_fill_gradientn(na.value="white",limits = c(3500,5000),
colours=c("yellow","orange","green","blue")) +
scale_y_continuous(expand = c(0,0)) +
scale_x_continuous(expand = c(0,0)) +
theme(panel.background = element_rect(fill = 'white',color="black"),
legend.key = element_blank()) +
coord_cartesian(xlim=c(-121, -113), ylim=c(31,35)) +
theme(panel.border = element_rect(colour = "gray50", fill=NA, size=1))
print(p1)
Upvotes: 2