How to DCmapR
Edward ‘Bingo’ LaHaye 2019-04-09
Hi and welcome to my first package, DCmapR. This package was first created in response to the 2nd annual hackathon at The Catholic University of America School of Engineering. Me and my team ran into the problem of plotting our points among the different wards and precincts of DC, and so this package was born from that struggle. This package will help you do a couple of things:
Get the shape files for the wards and precincts in DC
Get the data.frame coordinates and labels for all of the wards and precincts
Calculate the centroids for both wards and precincts so that you can easily label them
Create detailed and beautiful graphs of Washington, DC!
These objectives will be accomplished through each of their own functions that I will walk you through.
This is a pretty basic function that gives you either the shape data or
the dataframe data. To select the dataframe output just put
dataframe = TRUE as the argument, or you can leave it blank.
library(DCmapR) # For example lets get the dataframe for wards WardsDF <- get_Ward(dataframe = TRUE) # And you can easily plot this using ggplot2 mapOG <- ggplot() + geom_polygon(data = WardsDF, aes(x = long, y = lat, group = group, fill = factor(Ward)), col = "black", alpha = 0.3, size = 1) + scale_fill_discrete(name = "Ward") + coord_quickmap() mapOG
And if you want to you can use the shape file in the same way for
plotting, or you can also extract the data from it using
it. You can plot the SF as well it just can be a bit difficult in the
naming conventions, so i recommend sticking with the dataframe.
WardsSF <- get_Ward(dataframe = FALSE) WardsSFData <- data.frame(WardsSF) # but you can combine this for some nice maps :) library(dplyr) biggerset <- WardsDF %>% full_join(WardsSFData, by = c("Ward" = "WARD")) #You can then use this to make a nice little cloropleth map plot1 <- ggplot() + geom_polygon(data = biggerset, aes(x = long, y = lat, group = group, fill = as.numeric(as.character(POP_2010))), col = "black", alpha = 0.6, size = 1) + scale_fill_continuous(name = "Population \nin 2010") + theme(legend.title = element_text(size = 10)) + coord_quickmap() plot2 <- ggplot() + geom_polygon(data = biggerset %>% group_by(Ward), aes(x = long, y = lat, group = group, fill = as.numeric(as.character(UNEMPLOYME))), col = "black", alpha = 0.6, size = 1) + scale_fill_gradient(name = "Number of \nUnemployed", low = "blue", high = "red") + theme(legend.title = element_text(size = 10)) + coord_quickmap() plot1 plot2
Now as you can see from this, we can make nice looking graphs but we need labels for them! And my solution comes with the next function: get_centroid
get_centroid came about to help with labeling and getting those labels
into a pleasing spot for the wards. I wanted to get into the center for
each shape so I used
rgeos to get them. You can get
the centroids of either the Wards or Precincts depending if you select
FALSE for one of the options. Selecting neither will get you
nothing. Now lets get these labels on there!
Wardlabs <- get_centroid(Ward = TRUE) # And then you just add it in! plot1 + geom_text(data = Wardlabs, aes(x, y, label = Ward), size = 5)
plot2 + geom_text(data = Wardlabs, aes(x, y, label = Ward), size = 5)
Now there is a bit more information for the maps! The next step is to dive deeper into these wards and look into the precincts with in them.
This function was designed to get a better perspective on the wards
themselves and how their parts added up to the whole of DC. You can use
this function to give more detail to the map as a whole, or filter
through to get more detail on a singular ward.
only one parameter
dataframe = TRUE, which you can change to false for
PrecinctDF <- get_Precinct(dataframe = TRUE) #Take the first map we made and layer onto it mapOG + geom_polygon(data = PrecinctDF, aes(x = long, y = lat, group = group), inherit.aes = FALSE, fill = NA, colour = 'black') + ggtitle("DC with Wards and Precincts")
Along the development I came accross some roadblocks in zooming in with the precincts and wards as they don’t have labels for which Ward they belong in. So right now we are working on catagorizing all of the precincts so that they word properly with wards if you so wish to zoom in on each ward.
#Trim to ward 8, I'm not sure why its polygon number is 1 PrecinctSF <- get_Precinct(dataframe = FALSE) Ward1SF <- WardsSF[1,] Just1 <- PrecinctSF[Ward1SF, ] ggplot() + geom_polygon(data = Ward1SF, aes(x = long, y = lat, group = group)) + coord_quickmap()
#Use over to get the overlapping datapoints PrecinctSF <- get_Precinct(dataframe = FALSE) ggplot() + geom_polygon(data = Ward1SF, aes(x = long, y = lat, group = group), fill = "white") + geom_polygon(data = Just1, aes(x= long, y = lat, group = group), fill = NA, col = "black") + coord_quickmap() + ggtitle("Ward 8 with Precincts")
A refined precincts dataset will be in the next version of DCmapR. As you can see it gets pretty close, and with some tweaking could turn into a nice chloropleth map.
Overall I hope you enjoy using this package as I enjoyed developing it. All info was acquired from (via), so go get exploring that data as well if you are interested.