Add example of reading PostGIS data

README.md

@@ -11,7 +11,7 @@ This is a work in progress, any comments and suggestions are welcome!
 2. Reading coordinate information from text files (coming up..)
 3. Writing shapefiles (coming up..)
 3. [Getting data from MS Access database] (ReadingDataIntoR/GetDataFromMSAccess.R)
-4. Getting data from PostgreSQL database (coming up..)
+4. Getting data from PostgreSQL database (ReadingDataIntoR/GetDataFromPostGIS.R)
 
 ### Data processing and spatial analysis in R
 

ReadingDataIntoR/GetDataFromPostGIS.R

@@ -0,0 +1,62 @@
+#####################
+# Read PostGIS data to R
+#####################
+#
+# R script for reading PostGIS data for further processing
+# Ideas and info from:
+# - https://github.com/mablab/rpostgis
+# - https://cran.r-project.org/web/packages/rpostgis/rpostgis.pdf
+# - https://cran.r-project.org/web/packages/RPostgreSQL/RPostgreSQL.pdf
+# - https://cran.r-project.org/web/packages/sp/sp.pdf
+
+##----------------
+## PACKAGES
+##----------------
+
+#Install rpostgis and sp if needed and required dependencies
+#install.packages("rpostgis", "sp")
+
+#Load rpostgis
+library(rpostgis)
+
+#Load sp (Classes and Methods for Spatial Data)
+library(sp)
+
+
+##---------------
+## CONNECT TO POSTGIS DATABASE
+##---------------
+
+# Create connection (in the example you have a PostgreSQL server running on localhost and it has the database with the name osmtm)
+#Parameters
+#drv should be string "PostgreSQL"
+#dbname is name of the database
+#host is the DNS name of the host that runs the PostgreSQL server
+#port is the port where the PostgreSQL server is listening in
+#user is the username that has access to the database
+#password is the password for the user
+conn <- dbConnect("PostgreSQL",dbname='osmtm',host='localhost',port='5432',user='postgres',password='postgres')
+
+##---------------
+## READ DATA FROM THE POSTGIS DATABASE
+##---------------
+
+#read data with pgGetGeom from the database
+#Parameters
+#conn is the connection created above
+#name is a vector that has the schema name and table name elements
+#geom is the name of the geometry column in the table
+#other.cols is a vector that contains names of table columns to retrieve besides the geometry column
+tasks <- pgGetGeom(conn, name=c("public","task"), geom = "geometry", other.cols=c("project_id","date"))
+
+#view tasks as a string:
+str(tasks)
+
+#Quick visualization:
+plot(tasks)
+
+##---------------
+## DISCONNECT FROM THE POSTGIS DATABASE
+##---------------
+
+dbDisconnect(conn)