User Tools

Site Tools


spatial_analysis:sp_intro

The R ''sp'' package for spatial analysis

Importing data

Using rgdal or spgrass6 to import existing GIS data is probably the easiest way to get started. Both packages can also be used to export the results of your analysis back to a GIS environment.

An example using rgdal to import an ESRI Shapefile named points.shp located in the /home/steko/gisdata/ directory.

> library(rgdal)
> points <- readOGR(dsn="/home/steko/gisdata", layer="points")
OGR data source with driver: ESRI Shapefile 
Source: "/home/steko/gisdata", layer: "points"
with 61 features and 6 fields
Feature type: wkbPoint with 2 dimensions

Let's have a look at the imported data. Note that the points object is a SpatialPointsDataFrame.

> str(points)
Formal class 'SpatialPointsDataFrame' [package "sp"] with 5 slots
  ..@ data       :'data.frame':	61 obs. of  6 variables:
  .. ..$ RECNUM  : Factor w/ 61 levels "1","10","11",..: 1 12 23 34 45 56 59 60 61 2 ...
  .. ..$ NAME    : Factor w/ 61 levels "001","002","003",..: 1 2 3 4 5 6 7 8 9 10 ...
  .. ..$ LAT     : Factor w/ 61 levels "8023340.86","8023775.89",..: 19 5 10 9 13 16 17 20 22 31 ...
  .. ..$ LON     : Factor w/ 60 levels "715020.00","715327.00",..: 38 60 55 58 59 57 39 36 45 43 ...
  .. ..$ ALTITUDE: Factor w/ 37 levels "10","-115","16",..: 2 30 4 37 23 9 21 33 10 25 ...
  .. ..$ LONGNAME: Factor w/ 0 levels: NA NA NA NA NA NA NA NA NA NA ...
  ..@ coords.nrs : num(0) 
  ..@ coords     : num [1:61, 1:2] 747843 749457 749235 749365 749397 ...
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : NULL
  .. .. ..$ : chr [1:2] "coords.x1" "coords.x2"
  ..@ bbox       : num [1:2, 1:2] 715020 8023341 749457 8072390
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : chr [1:2] "coords.x1" "coords.x2"
  .. .. ..$ : chr [1:2] "min" "max"
  ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slots
  .. .. ..@ projargs: chr NA
spatial_analysis/sp_intro.txt · Last modified: 2012/11/30 09:59 (external edit)