ggplot2 maps with insets
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Here’s a quick demo of creating a map with an inset within it using ggplot. The inset is achieved using the gridExtra package.
Install libraries, set directory, read file
setwd("/Users/ScottMac/Dropbox/CANPOLIN_networks_ms/data") # change to your directory
library(ggplot2)
library(maps)
library(maptools)
library(gridExtra)
library(rgeos)
dat <- read.csv("siteinfo_blog.csv")
head(dat)
ecosystem lat lon
1 oak sav. 48.81 -123.6
2 oak sav. 48.79 -123.6
3 oak sav. 48.82 -124.1
4 oak sav. 48.82 -124.1
5 oak sav. 48.78 -123.9
6 oak sav. 48.78 -123.9
Get maps
# Get a map of Canada
canadamap <- data.frame(map("world", "Canada", plot = FALSE)[c("x", "y")])
# Get a map of smaller extent
canadamapsmall <- canadamap[canadamap$x < -90 & canadamap$y < 54, ]
Make the maps
# The inset map, all of Canada
a <- ggplot(canadamap) +
theme_bw(base_size = 22) +
geom_path(data = canadamap, aes(x, y), colour = "black", fill = "white") +
scale_size(guide="none") +
opts(panel.border = theme_rect(colour = 'black', size = 1, linetype=1),
panel.grid.major = theme_blank(), panel.grid.minor=theme_blank(),
panel.background = theme_rect( fill = 'white'),
legend.position = c(0.15,0.80), legend.key = theme_blank(),
axis.ticks = theme_blank(), axis.text.x=theme_blank(),
axis.text.y=theme_blank()) +
labs(x = '', y = '')
# The larger map, zoomed in, with the data
b <- ggplot(dat, aes(lon, lat, colour=ecosystem)) +
theme_bw(base_size = 22) +
geom_jitter(size=4, alpha=0.6) +
geom_path(data = canadamapsmall, aes(x, y), colour = "black", fill = "white") +
scale_size(guide="none") +
opts(panel.border = theme_rect(colour = 'black', size = 1, linetype=1),
panel.grid.major = theme_blank(), panel.grid.minor=theme_blank(),
panel.background = theme_rect( fill = 'white'),
legend.position = c(0.1,0.20), legend.text=theme_text(size=12, face='bold'),
legend.title=theme_text(size=12, face='bold'), legend.key = theme_blank(),
axis.ticks = theme_segment(size = 2)) +
labs(x = '', y = '')
Print the two maps together, one an inset of the other
This approach uses the gridExtra package for flexible alignment, etc. of ggplot graphs
grid.newpage()
vpb_ <- viewport(width = 1, height = 1, x = 0.5, y = 0.5) # the larger map
vpa_ <- viewport(width = 0.4, height = 0.4, x = 0.8, y = 0.8) # the inset in upper right
print(b, vp = vpb_)
print(a, vp = vpa_)
Written in Markdown, with help from knitr, and nice knitr highlighting/etc. in in RStudio.
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