Working with spatial and geometric operations in {sf}

Session 5

2023-09-27

1 Getting started

library(tidyverse)
library(sf)
library(tigris)
options(tigris_use_cache = TRUE)

options("tigris_use_cache" = TRUE)
us_states <- states()

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us_highways <- primary_roads()

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maryland <- filter(us_states, NAME == "Maryland")
lower48 <- filter(
  us_states,
  !(NAME %in%
    c(
      "United States Virgin Islands",
      "Commonwealth of the Northern Mariana Islands",
      "Guam",
      "Alaska",
      "American Samoa",
      "Puerto Rico",
      "Hawaii"
    ))
)

2 Converting objects between types

sfg <- st_point(c(-76.712838, 39.253383))

sfg

st_as_sfc(list(sfg))

Geometry set for 1 feature 
Geometry type: POINT
Dimension:     XY
Bounding box:  xmin: -76.71284 ymin: 39.25338 xmax: -76.71284 ymax: 39.25338
CRS:           NA

sfc <- st_as_sfc(list(sfg), crs = 4326)

sfc

Geometry set for 1 feature 
Geometry type: POINT
Dimension:     XY
Bounding box:  xmin: -76.71284 ymin: 39.25338 xmax: -76.71284 ymax: 39.25338
Geodetic CRS:  WGS 84

st_as_sf(sfc)

Simple feature collection with 1 feature and 0 fields
Geometry type: POINT
Dimension:     XY
Bounding box:  xmin: -76.71284 ymin: 39.25338 xmax: -76.71284 ymax: 39.25338
Geodetic CRS:  WGS 84
                           x
1 POINT (-76.71284 39.25338)

sf_df <- data.frame(
  name = "Example data frame",
  lon = -76.712838,
  lat = 39.253383
)

sf <- st_as_sf(
  sf_df,
  coords = c("lon", "lat"),
  crs = 4326
)

sf

Simple feature collection with 1 feature and 1 field
Geometry type: POINT
Dimension:     XY
Bounding box:  xmin: -76.71284 ymin: 39.25338 xmax: -76.71284 ymax: 39.25338
Geodetic CRS:  WGS 84
                name                   geometry
1 Example data frame POINT (-76.71284 39.25338)

3 Types of spatial operations

• Spatial filtering and topological relations
• Spatial joins and non-overlapping joins
• Spatial aggregation

Spatial filtering and topological relations

st_filter() defaults to intersecting geometries:

st_filter(
  us_states,
  maryland
)

Simple feature collection with 6 features and 15 fields
Geometry type: MULTIPOLYGON
Dimension:     XY
Bounding box:  xmin: -83.67539 ymin: 36.54085 xmax: -74.68956 ymax: 42.51607
Geodetic CRS:  NAD83
  REGION DIVISION STATEFP  STATENS GEOID     GEOIDFQ STUSPS
1      3        5      54 01779805    54 0400000US54     WV
2      3        5      24 01714934    24 0400000US24     MD
3      3        5      10 01779781    10 0400000US10     DE
4      1        2      42 01779798    42 0400000US42     PA
5      3        5      51 01779803    51 0400000US51     VA
6      3        5      11 01702382    11 0400000US11     DC
                  NAME LSAD MTFCC FUNCSTAT        ALAND     AWATER    INTPTLAT
1        West Virginia   00 G4000        A  62266513826  488918898 +38.6472854
2             Maryland   00 G4000        A  25151223822 6979843236 +38.9466584
3             Delaware   00 G4000        A   5046692239 1399219008 +38.9985661
4         Pennsylvania   00 G4000        A 115881476238 3397613881 +40.9046042
5             Virginia   00 G4000        A 102256342555 8529908321 +37.5222512
6 District of Columbia   00 G4000        A    158316181   18709785 +38.9042474
      INTPTLON                       geometry
1 -080.6183274 MULTIPOLYGON (((-77.75438 3...
2 -076.6744939 MULTIPOLYGON (((-75.756 39....
3 -075.4416440 MULTIPOLYGON (((-75.50949 3...
4 -077.8275233 MULTIPOLYGON (((-75.5931 39...
5 -078.6681938 MULTIPOLYGON (((-76.9159 36...
6 -077.0165167 MULTIPOLYGON (((-77.11975 3...

st_filter() can also support alternate topological relations:

st_filter(
  us_states,
  maryland,
  .predicate = st_disjoint
)

Simple feature collection with 50 features and 15 fields
Geometry type: MULTIPOLYGON
Dimension:     XY
Bounding box:  xmin: -179.2311 ymin: -14.60181 xmax: 179.8597 ymax: 71.43979
Geodetic CRS:  NAD83
First 10 features:
   REGION DIVISION STATEFP  STATENS GEOID     GEOIDFQ STUSPS           NAME
1       3        5      12 00294478    12 0400000US12     FL        Florida
2       2        3      17 01779784    17 0400000US17     IL       Illinois
3       2        4      27 00662849    27 0400000US27     MN      Minnesota
4       1        1      44 01219835    44 0400000US44     RI   Rhode Island
5       4        8      16 01779783    16 0400000US16     ID          Idaho
6       1        1      33 01779794    33 0400000US33     NH  New Hampshire
7       3        5      37 01027616    37 0400000US37     NC North Carolina
8       1        1      50 01779802    50 0400000US50     VT        Vermont
9       1        1      09 01779780    09 0400000US09     CT    Connecticut
10      4        8      35 00897535    35 0400000US35     NM     New Mexico
   LSAD MTFCC FUNCSTAT        ALAND      AWATER    INTPTLAT     INTPTLON
1    00 G4000        A 138965379385 45968913048 +28.3989775 -082.5143005
2    00 G4000        A 143778206717  6216848695 +40.1028754 -089.1526108
3    00 G4000        A 206244791203 18937236061 +46.3159573 -094.1996043
4    00 G4000        A   2677768885  1323681453 +41.5964850 -071.5264901
5    00 G4000        A 214050504522  2390996667 +44.3484222 -114.5588538
6    00 G4000        A  23190211616  1025871482 +43.6727945 -071.5841886
7    00 G4000        A 125935965771 13453455061 +35.5397100 -079.1308636
8    00 G4000        A  23872594714  1030642813 +44.0589536 -072.6710173
9    00 G4000        A  12541999507  1816115183 +41.5798637 -072.7466572
10   00 G4000        A 314198519809   726531289 +34.4346843 -106.1316181
                         geometry
1  MULTIPOLYGON (((-83.10874 2...
2  MULTIPOLYGON (((-87.89243 3...
3  MULTIPOLYGON (((-95.31991 4...
4  MULTIPOLYGON (((-71.67881 4...
5  MULTIPOLYGON (((-116.3584 4...
6  MULTIPOLYGON (((-70.83887 4...
7  MULTIPOLYGON (((-77.89977 3...
8  MULTIPOLYGON (((-72.04187 4...
9  MULTIPOLYGON (((-72.5279 41...
10 MULTIPOLYGON (((-103.0647 3...

Spatial joins

st_join(maryland, us_highways)

Simple feature collection with 466 features and 19 fields
Geometry type: MULTIPOLYGON
Dimension:     XY
Bounding box:  xmin: -79.48765 ymin: 37.88661 xmax: -74.98628 ymax: 39.72304
Geodetic CRS:  NAD83
First 10 features:
    REGION DIVISION STATEFP  STATENS GEOID     GEOIDFQ STUSPS     NAME LSAD
1        3        5      24 01714934    24 0400000US24     MD Maryland   00
1.1      3        5      24 01714934    24 0400000US24     MD Maryland   00
1.2      3        5      24 01714934    24 0400000US24     MD Maryland   00
1.3      3        5      24 01714934    24 0400000US24     MD Maryland   00
1.4      3        5      24 01714934    24 0400000US24     MD Maryland   00
1.5      3        5      24 01714934    24 0400000US24     MD Maryland   00
1.6      3        5      24 01714934    24 0400000US24     MD Maryland   00
1.7      3        5      24 01714934    24 0400000US24     MD Maryland   00
1.8      3        5      24 01714934    24 0400000US24     MD Maryland   00
1.9      3        5      24 01714934    24 0400000US24     MD Maryland   00
    MTFCC.x FUNCSTAT       ALAND     AWATER    INTPTLAT     INTPTLON
1     G4000        A 25151223822 6979843236 +38.9466584 -076.6744939
1.1   G4000        A 25151223822 6979843236 +38.9466584 -076.6744939
1.2   G4000        A 25151223822 6979843236 +38.9466584 -076.6744939
1.3   G4000        A 25151223822 6979843236 +38.9466584 -076.6744939
1.4   G4000        A 25151223822 6979843236 +38.9466584 -076.6744939
1.5   G4000        A 25151223822 6979843236 +38.9466584 -076.6744939
1.6   G4000        A 25151223822 6979843236 +38.9466584 -076.6744939
1.7   G4000        A 25151223822 6979843236 +38.9466584 -076.6744939
1.8   G4000        A 25151223822 6979843236 +38.9466584 -076.6744939
1.9   G4000        A 25151223822 6979843236 +38.9466584 -076.6744939
         LINEARID      FULLNAME RTTYP MTFCC.y                       geometry
1   1104258795090 Salisbury Byp     M   S1100 MULTIPOLYGON (((-75.756 39....
1.1 1103075320064 Salisbury Byp     M   S1100 MULTIPOLYGON (((-75.756 39....
1.2 1104258795072 Salisbury Byp     M   S1100 MULTIPOLYGON (((-75.756 39....
1.3 1104258845568 Salisbury Byp     M   S1100 MULTIPOLYGON (((-75.756 39....
1.4  110191599447 Salisbury Byp     M   S1100 MULTIPOLYGON (((-75.756 39....
1.5  110191599448 Salisbury Byp     M   S1100 MULTIPOLYGON (((-75.756 39....
1.6 1102149806067 Salisbury Byp     M   S1100 MULTIPOLYGON (((-75.756 39....
1.7 1102149813008 Salisbury Byp     M   S1100 MULTIPOLYGON (((-75.756 39....
1.8 1102149806121 Salisbury Byp     M   S1100 MULTIPOLYGON (((-75.756 39....
1.9 1102166635559 Salisbury Byp     M   S1100 MULTIPOLYGON (((-75.756 39....

Non-overlapping joins

st_is_within_distance() is an example of a non-overlapping join:

st_is_within_distance(us_highways, maryland, dist = units::set_units(100, "mi"))

Sparse geometry binary predicate list of length 17522, where the
predicate was `is_within_distance'
first 10 elements:
 1: (empty)
 2: (empty)
 3: (empty)
 4: (empty)
 5: (empty)
 6: (empty)
 7: (empty)
 8: (empty)
 9: (empty)
 10: (empty)

Filtering with spatial joins

You can use these joins for spatial filters using the base R syntax:

is_hwy_within_dist <- st_is_within_distance(
  us_highways,
  maryland,
  dist = units::set_units(100, "mi"),
  sparse = FALSE
)
us_highways[is_hwy_within_dist, ]

Simple feature collection with 2258 features and 4 fields
Geometry type: LINESTRING
Dimension:     XY
Bounding box:  xmin: -81.72573 ymin: 36.57507 xmax: -74.04969 ymax: 41.34626
Geodetic CRS:  NAD83
First 10 features:
          LINEARID      FULLNAME RTTYP MTFCC                       geometry
17  11013853809147 State Rte 611     S S1100 LINESTRING (-75.1366 40.350...
18  11013853809270 State Rte 611     S S1100 LINESTRING (-75.12634 40.28...
19  11013853809430 State Rte 611     S S1100 LINESTRING (-75.12603 40.28...
75  11013853864377  State Rte 29     S S1100 LINESTRING (-74.76432 40.20...
226  1105598256809  State Rte 26     S S1100 LINESTRING (-77.73622 40.89...
228  1108296536943  State Rte 26     S S1100 LINESTRING (-74.76814 40.20...
229  1108296536969  State Rte 26     S S1100 LINESTRING (-74.71174 40.27...
231  1104486135566  State Rte 26     S S1100 LINESTRING (-77.73356 40.89...
246  1108296538090 State Rte 129     S S1100 LINESTRING (-74.72239 40.18...
247  1108296538091 State Rte 129     S S1100 LINESTRING (-74.7224 40.183...

Filtering with spatial joins

Or using filter() if you use the name of the geomtery column (and convert the matrix output into a logical vector):

filter(
  us_highways,
  as.logical(st_is_within_distance(
    geometry,
    maryland,
    dist = units::set_units(100, "mi"),
    sparse = FALSE
  ))
)

Simple feature collection with 2258 features and 4 fields
Geometry type: LINESTRING
Dimension:     XY
Bounding box:  xmin: -81.72573 ymin: 36.57507 xmax: -74.04969 ymax: 41.34626
Geodetic CRS:  NAD83
First 10 features:
         LINEARID      FULLNAME RTTYP MTFCC                       geometry
1  11013853809147 State Rte 611     S S1100 LINESTRING (-75.1366 40.350...
2  11013853809270 State Rte 611     S S1100 LINESTRING (-75.12634 40.28...
3  11013853809430 State Rte 611     S S1100 LINESTRING (-75.12603 40.28...
4  11013853864377  State Rte 29     S S1100 LINESTRING (-74.76432 40.20...
5   1105598256809  State Rte 26     S S1100 LINESTRING (-77.73622 40.89...
6   1108296536943  State Rte 26     S S1100 LINESTRING (-74.76814 40.20...
7   1108296536969  State Rte 26     S S1100 LINESTRING (-74.71174 40.27...
8   1104486135566  State Rte 26     S S1100 LINESTRING (-77.73356 40.89...
9   1108296538090 State Rte 129     S S1100 LINESTRING (-74.72239 40.18...
10  1108296538091 State Rte 129     S S1100 LINESTRING (-74.7224 40.183...

Spatial aggregation

us_states_combine <- us_states |>
  group_by(DIVISION) |>
  summarise(
    geometry = st_combine(geometry)
  )

plot(us_states_combine[, 1])

4 Types of geometric operations

• Simplification
• Centroids
• Buffers
• Clipping (with or without subsetting)
• Unions
• Type transformations

Simplification

st_simplify(lower48, dTolerance = 100000)[, 1]

Simple feature collection with 49 features and 1 field (with 5 geometries empty)
Geometry type: GEOMETRY
Dimension:     XY
Bounding box:  xmin: -124.7989 ymin: 25.40562 xmax: -66.90256 ymax: 49.00013
Geodetic CRS:  NAD83
First 10 features:
   REGION                       geometry
1       3 POLYGON ((-78.36567 39.3604...
2       3 POLYGON ((-81.34136 25.4056...
3       2 POLYGON ((-89.45747 37.1908...
4       2 POLYGON ((-89.96571 47.2914...
5       3 POLYGON ((-75.78628 39.6205...
6       1       GEOMETRYCOLLECTION EMPTY
7       4 POLYGON ((-115.9605 47.8981...
8       1 POLYGON ((-70.9832 43.39448...
9       3 POLYGON ((-75.71132 36.2501...
10      1 POLYGON ((-71.58543 44.5129...

Centroids

plot(st_centroid(lower48)[, 1])

Buffers

plot(st_buffer(lower48, dist = 100)[, 1])

plot(st_buffer(lower48, dist = units::set_units(100, "mi"))[, 1])

Clipping (with or without subsetting)

plot(st_intersection(us_highways, maryland)[, 1])

Unions

us_highways_union <- us_highways |>
  group_by(RTTYP) |>
  summarise(
    geometry = st_union(geometry)
  )

plot(us_highways_union[, 1])

Type transformations

plot(st_cast(us_highways[1, ], to = "POINT"))