I am having trouble getting data labels to display over the provinces in a GADM
map of Canada.
Specifically, I need the variable "Number" from the data set "by_province",
grouped by "region", to appear on the corresponding regions of the map.
The data set "by_province" looks like this:
long lat order hole piece region
group Number
-110.37074 60.00006 1 FALSE 1 Alberta
Alberta.1 132
-110.36250 60.00006 2 FALSE 1 Alberta
Alberta.1 132
-110.35103 60.00006 3 FALSE 1 Alberta
Alberta.1 132
and the data set "tract" is the map data without the "Number" variable.
I looked into working this out from by researching the geom_map function here:
http://ggplot2.tidyverse.org/reference/geom_map.html
my code looks like this:
# get the raw map data
can_map <- getData('GADM', country = "CAN", level = 1) # download map level
with provinces
tract <- fortify(can_map, region = "NAME_1") # transforms data from shapefiles
into a dataframe that ggplot can understand, from
http://www.kevjohnson.org/making-maps-in-r/
# create subsets of the kcj data if needed, for example by year
kids_data_2017 <- subset(kids_data, year == 2017) # data for the year 2017
kids_data_2018 <- subset(kids_data, year == 2018) # data for the year 2018
# extract the needed data
kids_province_data <-
data.table::data.table(kids_data_2017$Province_Territory__c,
kids_data_2017$Number_of_kids__c)
names(kids_province_data)[1] <- "Province"
names(kids_province_data)[2] <- "Number"
# sum the data by province
kids_province_sums <- aggregate(.~Province, data = kids_province_data, sum)
# join the data to the map
names(tract)[6] <- "region"
names(kids_province_sums)[1] <- "region"
by_province <- left_join(tract, kids_province_sums)
# create the data map
kids_map <- ggplot(by_province, aes(map_id = region)) + #plots the
map in by_province separating by region
geom_map(aes(fill = Number), #generates
aestheticsa for the plot
map = tract, #takes
the data from tract
color = "#ffffff", #makes
the color of the borders between regions white
size = 0.15) + #sets
the thickness of the boarder lines
coord_map("polyconic") + #sets the
coordinates to polyconic (rounded lat and long)
scale_fill_gradient(name = "Children Reached", #sets the
gradient of the value scale: names the scale
low = grey_2, #color
of the low end
high = orange_1) + #color
of the high end
expand_limits(x = tract$long, #ensure
limits include all values for all plots
y = tract$lat) +
labs(x = NULL, #add
labels, no x title
y = NULL, #no y
title
title = "Number of Children Reached by Province", #map
title
subtitle = "2017") + #map
subtitle
geom_text(data = by_province, #add a text
layer
aes(long,
#aethetics for the text, x axis
lat, #y
axis
label = Number,
#the value to display
size=3)) +
#size of the text
theme(axis.ticks = element_blank(), #theme of
the graph, no axis ticks
axis.text = element_blank(), #no
axis text
panel.background = element_blank(), #blank
background
panel.border = element_blank()) #blank
border
# save as png
ggsave(kids_map, file = "kids_map.png", width = 6, height = 4.5, type =
"cairo-png”)
I have asked this question on stack overflow, and was refered to this answer:
https://stackoverflow.com/questions/9441436/ggplot-centered-names-on-a-map
The solution there did not fix my problem, though it did get me closer.
The solution on that post is using a single vector of labels.
My post on stackoverflow has images of my output:
https://stackoverflow.com/questions/49118323/labelling-a-map-plotted-with-geom-map
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