Trying to map petition data in R - r

Question

I am trying to map a UK government petition data in R. I used the boundary data from ONS geography portal. The code works and the first map I created also works.
#Install packages
install.packages("tidyverse")
install.packages("jsonlite")
install.packages("geojsonio")
install.packages("sp")
install.packages("parlitools")
install.packages("rvest")
install.packages("xml2")
install.packages("magrittr")
#Load packages
library(tidyverse)
library(jsonlite)
library(geojsonio)
library(sp)
library(parlitools)
library(rvest)
library(xml2)
library(magrittr)
[#GETTING PETITION DATA
#Importing petition for UK-wide lockdown from JSON format
petition <- fromJSON("https://petition.parliament.uk/petitions/301397.json", flatten = TRUE)
signatures <- petition$data$attributes$signatures_by_constituency %>%
rename(constituency = name)
#MAPPING BOUNDARIES
#Save url for boundary data UK
url <- "https://opendata.arcgis.com/datasets/b64677a2afc3466f80d3d683b71c3468_0.geojson"
#Load and save the boundary data as uk_map
uk_map <- geojson_read (url, what = "sp")
#pcon18cd is code name for constituency (as we can see when we view uk_map). Use fortify to get this data.
fort_uk_map <- fortify(uk_map, region = "pcon18cd")
#MAPPING PETITION DATA
#Join map data to signatures data from constituency using left_join
full_uk_map <- left_join(fort_uk_map, signatures, by = c("id" = "ons_code"))
#Plot-1a: Map of signatures in the whole of UK
ggplot() +
geom_polygon(data = full_uk_map, aes(x = long, y= lat, group = group, fill = signature_count)) +
geom_path(color = "black", size = 0.1) +theme(legend.position = "bottom") +
theme_void() +
labs(x = NULL,
y = NULL,
title = "Signatories of the UK Coronavirus Lockdown Petition",
subtitle = "Let's investigate where the signatures come from",
caption = "Geometries: ONS Open Geography Portal; Data: UK Parliament and Government",
fill = "Signature Count")][1]
But, as you can see from the image, the higher signatures have a lighter color. I would like to change it so that the higher number of signatures have a darker color.
So, I tried this code just below the above code and that's where I am facing issues.
#Change color of legend so that higher signature count equals darker color. Use quantile () [Doesn't work]
no_of_classes <- 9
quantiles <- quantile(full_uk_map$signature_count, probs = seq(0, 1, length.out = no_of_classes + 1))
labels <- c()
for(band in 1:length(quantiles)){
labels <- c(labels, paste0(round(quantiles[band])," - ", round(quantiles[band + 1])))
}
full_uk_map$quantiles <- cut(full_uk_map$signature_count, breaks = quantiles, labels = labels,
include.lowest = T)
labels <- labels[1:length(labels)-1]
#Plot-1b: Map of signatures in the whole of UK [Doesn't work]
sig_map_by_quantile <- ggplot() +
geom_polygon(data = full_uk_map, aes(x = long, y = lat, group = group, fill = quantiles)) +
geom_path(color = "black", size = 0.1) +
scale_fill_brewer(type = 'qual', palette = "Blues", guide = "legend", name = "Signature Count", labels = labels) +
theme_void +
theme(legend.position = "bottom") +
labs(x = NULL,
y = NULL,
title = "Signatories of the UK Coronavirus Lockdown Petition",
caption = "Geometries: ONS Open Geography Portal; Data: UK Parliament and Government")
When I run the full_uk_map$quantiles, this is the error message I see:
> full_uk_map$quantiles <- cut(full_uk_map$signature_count, breaks = quantiles, labels = labels,
+ include.lowest = T)
Error in cut.default(full_uk_map$signature_count, breaks = quantiles, :
lengths of 'breaks' and 'labels' differ
Would anyone be able to help? Much appreciated!

Answer 1

Why you made us go through all that package installation, downloading files from the Internet, fortification, merging, and then waiting for the plot to appear is beyond me.
All you had to ask was why the cut function was returning an error. Your title is totally irrelevant to the problem.
Anyway, the cut function, although not mentioned in the documentation (which is a shame if true), requires that the length of labels be one less than the length of breaks, if breaks is specified as a vector. Apologies to all if this is in fact mentioned in the documentation, but I didn't see it after a good long look. It may be hidden between the lines of the descriptions for the breaks and labels arguments. Note that the breaks argument can be provided as a number (of break-points) or, as in your case, a vector of cut-points.
For example, if breaks = c(1,2,3), then that implies you have two intervals, so you need 2 labels.
In your code, you supply the quantiles vector as the breaks and labels vector and the labels. Both have the same length, which triggers the error; you have 1 too many labels. Solution: make the length of labels one less than the length of breaks.