Membaca data spasial

Memvisualisasikan Data Geospasial di R

Charlotte Wickham

Assistant Professor at Oregon State University

Pendapatan median di County New York

Traktus sensus adalah area dengan jumlah penduduk kira-kira sama
Objek spasial:
- Poligon traktus sensus
- Poligon lingkungan yang lebih besar
- Poligon area perairan

Peta NYC

Prosedur

Baca shapefile yang mendeskripsikan lingkungan dan perairan
Samakan dua sistem koordinat berbeda
Gabungkan data dari data frame ke SpatialPolygonsDataFrame
Percantik peta hingga siap publikasi

Peta NYC

Membaca shapefile

Data vektor: data berupa titik, garis, poligon
Shapefile adalah format paling umum

Membaca shapefile

# rgdal::readOGR() membaca format vektor
library(rgdal) 
library(sp)

dir()

"water"

dir("water")

"water-areas.dbf" "water-areas.prj" 
"water-areas.shp" "water-areas.shx"

water <- readOGR("water", "water-areas")

OGR data source with driver: ESRI Shapefile 
Source: "water", layer: "water-areas"
dengan 20 fitur
Memiliki 5 field

Memeriksa hasil

summary(water)

Object of class SpatialPolygonsDataFrame
Coordinates:
        min       max
x -74.04731 -73.90866
y  40.68419  40.88207
Is projected: FALSE 
...

plot(water)

Garis NYC

Membaca berkas raster

library(rgdal)  # rgdal::readGDAL() membaca format raster ke objek sp
library(raster) # raster::raster() membaca format raster ke objek raster

dir()

"usgrid_data_2000"   "usgrid_data_2000_1"

dir("usgrid_data_2000")

"metadata"     "usarea00.tif"  "usba00.tif" "usfb00.tif" "usgrid-2000-variables.xls" "usp2500.tif" 
"uspop300.tif" "uspov00.tif"  "uspvp00.tif"

total_pop <- raster("usgrid_data_2000/uspop300.tif")

Memeriksa hasil

total_pop

class       : RasterLayer 
dimensions  : 3120, 7080, 22089600  (nrow, ncol, ncell)
resolution  : 0.008333333, 0.008333333  (x, y)
extent      : -125, -66, 24, 50  (xmin, xmax, ymin, ymax)
coord. ref. : +proj=longlat +datum=NAD83 +no_defs +ellps=GRS80 +towgs84=0,0,0 
data source : /Users/wickhamc/Documents/Projects/courses-visualizing-geospatial-
              data-in-r/data/census_grids/usgrid_data_2000/uspop300.tif 
names       : uspop300 
values      : 0, 65535  (min, max)

Ayo berlatih!

Memvisualisasikan Data Geospasial di R