Adding data to spatial objects

Visualizing Geospatial Data in R

Charlotte Wickham

Assistant Professor at Oregon State University

Income data from ACS

str(nyc_income)

'data.frame':    288 obs. of  6 variables:
 $ name    : chr  "Census Tract 1, New York County, New York" 
 "Census Tract 2.01, New York County, New York" 
 "Census Tract 2.02, New York County, New York" 
 "Census Tract 5, New York County, New York" ...
 $ state   : int  36 36 36 36 36 36 36 36 36 36 ...
 $ county  : int  61 61 61 61 61 61 61 61 61 61 ...
 $ tract   : chr  "000100" "000201" "000202" "000500" ...
 $ estimate: num  NA 23036 29418 NA 18944 ...
 $ se      : num  NA 3083 1877 NA 1442 ...

Tract polygon data

str(nyc_tracts, max.level = 2)

Formal class 'SpatialPolygonsDataFrame' [package "sp"] with 5 slots
  ..@ data       :'data.frame':    288 obs. of  9 variables:
  ..@ polygons   :List of 288
  .. .. [list output truncated]
  ..@ plotOrder  : int [1:288] 175 225 97 209 249 232 208 247 244 207 ...
  ..@ bbox       : num [1:2, 1:2] -74 40.7 -73.9 40.9
  .. ..- attr(*, "dimnames")=List of 2
  ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slot

Tract polygon data

str(nyc_tracts@data)

'data.frame':    288 obs. of  9 variables:
 $ STATEFP : chr  "36" "36" "36" "36" ...
 $ COUNTYFP: chr  "061" "061" "061" "061" ...
 $ TRACTCE : chr  "001401" "002201" "003200" "004000" ...
 $ AFFGEOID: chr  "1400000US36061001401" "1400000US36061002201" 
 "1400000US36061003200" "1400000US36061004000" ...
 $ GEOID   : chr  "36061001401" "36061002201" "36061003200" "36061004000" ...
 $ NAME    : chr  "14.01" "22.01" "32" "40" ...
 $ LSAD    : chr  "CT" "CT" "CT" "CT" ...
 $ ALAND   : num  93510 161667 217682 178340 124447 ...
 $ AWATER  : num  0 0 0 0 0 0 0 0 0 0 ...

Goal: Add the estimated median income to this data frame

Correspondence between polygons and data

four_tracts

class       : SpatialPolygons 
features    : 4 
extent      : -73.99022, (xmin)
              -73.97875, (xmax)
              40.71413,  (ymin)
              40.73329   (ymax)
coord. ref. : +proj=longlat +datum=NAD83
              +no_defs +ellps=GRS80 
              +towgs84=0,0,0

sapply(four_tracts@polygons,
       function(x) x@ID)

"156" "157" "158" "159"

four_data

    TRACTCE
159  004000
158  003200
157  002201
156  001401

Correspondence between polygons and data

SpatialPolygonsDataFrame(Sr, data, match.ID = TRUE)

SpatialPolygonsDataFrame(four_tracts, four_data)

class       : SpatialPolygonsDataFrame 
features    : 4 
extent      : -73.99022, -73.97875, 40.71413, 40.73329  (xmin, xmax, ymin, ymax)
coord. ref. : +proj=longlat +datum=NAD83 +no_defs +ellps=GRS80 +towgs84=0,0,0 
variables   : 1
names       : TRACTCE 
min values  :  001401 
max values  :  004000

Correspondence between polygons and data

SpatialPolygonsDataFrame(Sr, data, match.ID = TRUE)

SpatialPolygonsDataFrame(four_tracts, four_data)@data

    TRACTCE
156  001401
157  002201
158  003200
159  004000

Correspondence between polygons and data

SpatialPolygonsDataFrame(four_tracts, four_data, match.ID = FALSE)@data

    TRACTCE
159  004000
158  003200
157  002201
156  001401

Correspondence is now lost!

Adding new data

Once created, no checks that data stay matched to polygons
Recreate object being very careful to match polygons to the right rows
sp::merge(),merge() for sp objects

Let's practice!

Visualizing Geospatial Data in R