In 1992, Rusty Dodson and Waldo Tobler digitized John Snow’s cholera map. Unfortunately, Dodson and Tobler did not include the names of roads (e.g., Broad Street) in their data set. While not strictly necessary for analysis or visualization, having the names will be useful to some. To that end, I append the actual street names, taken from the map itself, to the data. This appended data set is called roads.
Before discussing names, some discussion of the structure of roads is warranted. The data contain 1241 pairs of x-y coordinates. These coordinates define the endpoints of the straight line segments used to describe 528 numerically identified “streets”.
head(roads)
#> street n x y id name
#> 1 1 2 16.73800 18.69600 1 Map Frame
#> 2 1 2 17.66000 18.71200 2 Map Frame
#> 3 2 2 14.46200 18.65500 3 Map Frame
#> 4 2 2 16.73800 18.69600 4 Map Frame
#> 5 3 2 12.79388 18.61613 5 Map Frame
#> 6 3 2 14.46200 18.65500 6 Map Frame
nrow(roads)
#> [1] 1241
length(unique(roads$street))
#> [1] 528These 528 “streets” do not correspond to real-world streets. Excluding the 50 “streets” used to describe the map’s frame, the remaining 478 “streets” describe 206 “real-world” roads (e.g., Oxford Street, Regent Street). This discrepancy emerges because 40% of “real-world” roads are composed of multiple “street” segments. For example, Oxford Street consists of 26 line segments and Broad Street consists of 6.
# Map Border "Streets" #
top <- c(1:12, 14)
right <- c(37, 62, 74, 142, 147, 205, 240, 248, 280, 360, 405, 419, 465)
bottom <- c(483, seq(487, 495, 2), 498, 500, seq(503, 519, 2))
left <- c(31, 79, 114, 285, 348, 397, 469)
border <- sort(c(bottom, left, top, right))
length(border)
#> [1] 50The primary source for road names is Snow’s map. A high resolution version is available here. While great effort was made to correctly record and cross-reference names, there may still be errors. Error reports and suggestions for amendments are welcome.
Some roads on the map do not have a name. In those cases, I attached unique labels like “Unknown-D”.
Some names appear multiple times even though they lie at different locations. For these, I use Roman numerals to distinguish them (e.g., “King Street (I)” and “King Street (II)”).
There is one apparent coding error in Dodson and Tobler’s road data. Queen Street (I) extends too far: the water pump (#5) that is clearly located on Marlborough Mews (see map, cited above), ends up on Queen Street (I).
I amend this by moving the end point of Queen Street (I) westward so that the street only runs north-south. I do so by reassigning the segment that runs east-west to be part of Marlborough Mews.
snow.streets <- HistData::Snow.streets
snow.streets$id <- seq_len(nrow(snow.streets))
# Data frame of road names
road.data <- read.csv("~/Documents/Data IV/Snow/road3b.csv",
stringsAsFactors = FALSE)
roads <- merge(snow.streets, road.data, by = "street", all.x = TRUE)
roads[is.na(roads$name), "name"] <- "Map Frame"
roads[roads$id == 277, "street"] <- 116
roads[roads$id == 277, "name"] <- "Marlborough Mews"
roads[roads$id == 277, c("x", "y")] <- roads[roads$id == 276, c("x", "y")]
roads[roads$name == "Queen Street (I)", "n"] <- 4
roads[roads$name == "Marlborough Mews", "n"] <- 3
roads <- roads[order(roads$id), ]To help locate and visualize streets and road segments (including map frame segments), you can use the streetNameLocator(), streetNumberLocator(), or segmentLocator().
Note that streetNameLocator() uses the names in the roads data set. However, the function tries to corrects for case and removes extraneous spaces: streetNameLocator(“Oxford Street”) and streetNameLocator(“oxford street”).
segmentLocator() is for those interested in more granular analysis. It uses individual road segments as the unit of observation.
There are 206 “valid” road names; 207, if we include “Map Frame”:
| 1 -70 | 71 - 140 | 141 - 207 |
|---|---|---|
| Adam and Eve Court | Greek Street | Phoenix Yard |
| Air Street | Green Dragon Yard | Picadilly |
| Albany Street | Greens Court | Plough Yard |
| Albemarle Street | Ham Yard | Poland Street |
| Allens Court | Hanover Street | Pollen Street |
| Angel Court | Hanway Street | Portland Mews |
| Archer Street | Haymarket | Portland Street |
| Argyll Place | Heddon Court | Princes Street (I) |
| Argyll Street | Heddon Street | Princes Street (II) |
| Arundel Place | Hollen Street | Princes Street (III) |
| Arundel Street | Hopkins Street | Princes Street/Hanover Square |
| Batemans Buildings | Jermyn Street | Pulteney Court (I) |
| Beak Street | John Street | Pulteney Court (II) |
| Bentinck Street | Kemps Court | Queen Street (I) |
| Berners Street | King Street (I) | Queen Street (II) |
| Berwick Street | King Street (II) | Queen Street (III) |
| Black Lion Court | Kings Arms Yard | Queens Head Court |
| Blenheim Mews | Leicester Street (I) | Rathbone Place |
| Blenheim Street | Leicester Street (II) | Regent Street |
| Boyle Street | Lisle Street | Regents Quadrant |
| Brewer Street | Little Argyll Street | Richmond Buildings/Mews |
| Bridle Street | Little Chapel Street | Richmond Street |
| Broad Street | Little Crown Court | Rupert Street |
| Bruton Street | Little Dean Street | Sackville Street |
| Bull Yard | Little Marlborough Street | Saville Row |
| Burlington Arcade | Little Pulteney Street | Sherrard Street |
| Burlington Gardens | Little Windmill Street | Ship Yard |
| Cambridge Street | Lower James Street | Sidney Alley |
| Carlisle Street | Lower John Street | Silver Street |
| Carnaby Court | Lowndes Court | Smiths Court/Yard |
| Carnaby Street | Macclesfield Street | Soho Square |
| Castle Street East | Macclesfield Street/Gerrard Street | South Row |
| Catherine Wheel Yard | Maddox Street | St Anns Court |
| Chapel Place | Maidenhead Court | St Anns Place |
| Charles Street | Map Frame | St James Workhouse |
| Church Street | Margaret Court | Sutton Street |
| Clifford Street | Margaret Street | Swallow Place |
| Coach & Horses Yard | Market Court | Swallow Street |
| Cock Court | Market Place | Tichborne Street |
| Conduit Street | Market Row | Titchfield Street |
| Cork Mews | Market Street | Turks Head Yard |
| Cork Street | Marlborough Court | Tyler Court |
| Coventry Street | Marlborough Mews | Tyler Street |
| Cross Street | Marlborough Row | Tylers Court |
| Crown Court | Marshall Street | Unknown-A1 |
| Dean Street | Marylebone Street | Unknown-A2 |
| Dover Street | Masons Arms Yard | Unknown-B |
| Duck Lane/Ham Square | Meards Court/Street | Unknown-C |
| Dufours Place | Mill Street | Unknown-D |
| Edward Street | Nags Head Yard | Unknown-E |
| Falconberg Court | Naylors Yard | Unknown-F |
| Falconberg Mews | New Bond Street | Upper James Street |
| Fouberts Place | New Burlington Mews | Upper John Street |
| Francis Street | New Burlington Street | Upper Rupert Street |
| Frith Street | New Street | Vigo Street |
| George Court (I) | New Street/Husband Street | Vine Street |
| George Court (II) | Newman Street | Walkers Court |
| George Place | Noel Street | Wardour Mews |
| George Street | Norris’s Place | Wardour Street |
| George Yard | North Coventry Street | Warwick Street |
| Glasshouse Street | Old Burlington Mews | Wellington Mews |
| Golden Place | Old Burlington Street | Wells Street |
| Golden Square | Old Compton Street | West Street |
| Grafton Street | Orchard Place | Whitcomb Court |
| Great Castle Street | Oxendon Street | White Bear Yard |
| Great Chapel Street | Oxford Street | William and Mary Yard |
| Great Crown Court | Panton Street | Winsley Street |
| Great Marlborough Street | Perrys Place | |
| Great Pulteney Street | Peter Street | |
| Great Windmill Street | Pews Place |
The original map is 14.5 x 15.5 inches with a stated nominal scale of 30 inches per mile.
Dodson and Tobler write that “The scale of the source map is approx. 1:2000. Coordinate units are meters.” By my calculation one unit on the map is approximately 177 feet or 54 meters per unit.1
According to Dodson and Tobler’s street data, the length of Carnaby Street from its intersection with Great Marlborough to its intersection with Silver Street is 2.61 units. According to Google Maps, the approximate analog of that segment is the distance along parts of Great Marlborough Street and Carnaby Street between 19-21 Great Marlborough Street and 43 Carnaby Street (at Ganton Street): 463 ft. This translates into approximately 177 feet/unit or 54 meters/unit.↩