8  Reading, Exploring, and Visualising Spatial Data with sf (Cont. Chapter 6)

8.1 Package

8.2 Data

columbus <- st_read(system.file("shapes/columbus.gpkg", package="spData")[1], quiet=TRUE)
columbus
Simple feature collection with 49 features and 20 fields
Geometry type: POLYGON
Dimension:     XY
Bounding box:  xmin: 5.874907 ymin: 10.78863 xmax: 11.28742 ymax: 14.74245
Projected CRS: Undefined Cartesian SRS with unknown unit
First 10 features:
       AREA PERIMETER COLUMBUS_ COLUMBUS_I POLYID NEIG  HOVAL    INC     CRIME
1  0.309441  2.440629         2          5      1    5 80.467 19.531 15.725980
2  0.259329  2.236939         3          1      2    1 44.567 21.232 18.801754
3  0.192468  2.187547         4          6      3    6 26.350 15.956 30.626781
4  0.083841  1.427635         5          2      4    2 33.200  4.477 32.387760
5  0.488888  2.997133         6          7      5    7 23.225 11.252 50.731510
6  0.283079  2.335634         7          8      6    8 28.750 16.029 26.066658
7  0.257084  2.554577         8          4      7    4 75.000  8.438  0.178269
8  0.204954  2.139524         9          3      8    3 37.125 11.337 38.425858
9  0.500755  3.169707        10         18      9   18 52.600 17.586 30.515917
10 0.246689  2.087235        11         10     10   10 96.400 13.598 34.000835
       OPEN    PLUMB DISCBD     X     Y NSA NSB EW CP THOUS NEIGNO
1  2.850747 0.217155   5.03 38.80 44.07   1   1  1  0  1000   1005
2  5.296720 0.320581   4.27 35.62 42.38   1   1  0  0  1000   1001
3  4.534649 0.374404   3.89 39.82 41.18   1   1  1  0  1000   1006
4  0.394427 1.186944   3.70 36.50 40.52   1   1  0  0  1000   1002
5  0.405664 0.624596   2.83 40.01 38.00   1   1  1  0  1000   1007
6  0.563075 0.254130   3.78 43.75 39.28   1   1  1  0  1000   1008
7  0.000000 2.402402   2.74 33.36 38.41   1   1  0  0  1000   1004
8  3.483478 2.739726   2.89 36.71 38.71   1   1  0  0  1000   1003
9  0.527488 0.890736   3.17 43.44 35.92   1   1  1  0  1000   1018
10 1.548348 0.557724   4.33 47.61 36.42   1   1  1  0  1000   1010
                             geom
1  POLYGON ((8.624129 14.23698...
2  POLYGON ((8.25279 14.23694,...
3  POLYGON ((8.653305 14.00809...
4  POLYGON ((8.459499 13.82035...
5  POLYGON ((8.685274 13.63952...
6  POLYGON ((9.401384 13.5504,...
7  POLYGON ((8.037741 13.60752...
8  POLYGON ((8.247527 13.58651...
9  POLYGON ((9.333297 13.27242...
10 POLYGON ((10.08251 13.03377...

8.3 Explore data structure

st_crs(columbus)
Coordinate Reference System:
  User input: Undefined Cartesian SRS with unknown unit 
  wkt:
ENGCRS["Undefined Cartesian SRS with unknown unit",
    EDATUM["Unknown engineering datum"],
    CS[Cartesian,2],
        AXIS["x",unspecified,
            ORDER[1],
            LENGTHUNIT["unknown",0]],
        AXIS["y",unspecified,
            ORDER[2],
            LENGTHUNIT["unknown",0]]]
sf::st_geometry(columbus)
Geometry set for 49 features 
Geometry type: POLYGON
Dimension:     XY
Bounding box:  xmin: 5.874907 ymin: 10.78863 xmax: 11.28742 ymax: 14.74245
Projected CRS: Undefined Cartesian SRS with unknown unit
First 5 geometries:

8.4 Visualise data

st_geometry() is an sf function that extracts only the geometry from an sf object.

st_geometry(columbus)
Geometry set for 49 features 
Geometry type: POLYGON
Dimension:     XY
Bounding box:  xmin: 5.874907 ymin: 10.78863 xmax: 11.28742 ymax: 14.74245
Projected CRS: Undefined Cartesian SRS with unknown unit
First 5 geometries:
plot(st_geometry(columbus))

Your turn: Use ggplot2 to draw the plot