Introduction to spatial data analysis in r
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This document provides an outline and overview of spatial data analysis in R. It introduces the installation of spatial packages in R, importing and exporting spatial data, and creating different types of spatial objects like points, lines, and polygons. It provides examples of how to create spatial point, line, and polygon objects from x-y coordinate data and manipulate their properties. These include assigning coordinate reference systems, plotting the spatial objects, and summarizing their characteristics. The document aims to demonstrate fundamental spatial analysis tasks in R.
Introduction to spatial data analysis in r
- 1. INTRODUCTION TO SPATIAL DATA ANALYSIS IN R Richard W Wamalwa1 - MSc., MBA(Finance), BSc. 1Directorate of Academic Quality Assurance, JKUAT 2011 RM 610-Environmental, Spatial, GIS, 2011
- 2. OUTLINE Installation of Sp in R Data export into R Creating spatial patterns/spatial points Changing the coordinate referencing system Creating a SpatialPointsDataframe Creating and manipulating SpatialLines objects Create the Polygon Objects References
- 3. ID x y z 1 1 1 21 2 1 2 20 3 1 3 20 4 1 4 21 5 2 3 24 6 3 2 21 7 3 6 21 8 3 7 23 9 4 1 19 10 4 3 21 11 4 4 24 12 4 7 18 13 5 6 21 14 6 2 18 15 6 7 25 16 7 3 20 17 7 5 17
- 6. SPATIAL POINT CONTD x1<-c(2,4,8,3,6,9,2,3,7,9,4,6,8,6,8) y1<-rep(seq(2,6),c(3,3,4,3,2)) data<-data.frame(x1,y1) data1<-data attach(data1) coordinates(data1)<-~x1+y1 summary(data1) class(data1) str(data1) bbox(data1) proj4string(data1) coordinates(data1)
- 7. CHANGING THE COORDINATE REFERENCING SYSTEM crsnew<-CRS("+proj=longlat +ellps=WGS84") data2<-SpatialPoints(data,proj4string =crsnew) class(data2) summary(data2) plot(data1,axes=TRUE,col="red",pch=1) plot(data1,axes=TRUE,col="blue",pch="+")
- 8. CREATING A SPATIALPOINTSDATAFRAME x2<-c(1,2,3,3,4,4,5,5,6,6,7) y2<-rep(seq(2,6),c(1,4,2,2,2)) z2<-c(10,30,45,60,70,100,80,130,150,170,190) data3<-data.frame(x2,y2,z2) Converting to spatial plot(s) gridded(s) <- TRUE gridded(s) class(s)
- 9. SPATIALPOINTSDATAFRAME CONTD summary(s) plot(s) gridded(s) <- FALSE gridded(s) class(s) # data.frame data(meuse.grid) coordinates(meuse.grid) <- ~x+y gridded(meuse.grid) <- TRUE plot(meuse.grid) # not much good summary(meuse.grid)
- 10. #CREATING AND MANIPULATING SPATIALLINES OBJECTS x1=cbind(c(1,5,8),c(1,4,8)) x2=cbind(c(1,9),c(4,2)) x3=cbind(c(3,9),c(1,4)) L1 = Lines(list(Line(x1)), ID="N1") L2 = Lines(list(Line(x2)), ID="N2") L3 = Lines(list(Line(x3)), ID="M3") mylines= SpatialLines(list(L1,L2,L3)) plot(mylines,axes=T,grid=T)
- 11. SPATIALLINES OBJECTS CONTD x1=cbind(rnorm(n),rnorm(n,0,0.25)) x2=cbind(rnorm(n),rnorm(n,0,0.25)) x3=cbind(rnorm(n),rnorm(n,0,0.25)) L1=Lines(list(Line(x1)),ID="mp1") L2=Lines(list(Line(x2)),ID="mp2") L3=Lines(list(Line(x3)),ID="mp3") s=SpatialLines(list(L1,L2,L3)) plot(s,axes=T)
- 12. #CREATE THE POLYGON OBJECTS #Step 1: Create the Polygon Objects Sr1 = Polygon(cbind(c(2, 4, 4, 1, 2), c(2, 3, 5, 4, 2))) Sr2 = Polygon(cbind(c(5, 4, 2, 5), c(2, 3, 2, 2))) Sr3 = Polygon(cbind(c(4, 4, 5, 10, 4), c(5, 3, 2, 5, 5))) Sr4 = Polygon(cbind(c(5, 6, 6, 5, 5), c(4, 4, 3, 3, 4)), hole = TRUE) #Step 2: Creating Srs1 = Polygons(list(Sr1), "s1") Srs2 = Polygons(list(Sr2), "s2") Srs3 = Polygons(list(Sr3, Sr4), "s3/4") #Step 3: Creating a SpatialPolygons list object SpP = SpatialPolygons(list(Srs1, Srs2, Srs3), 1:3) plot(SpP, col = 1:3, pbg = "white")
- 13. REFERENCES Gentleman, R., Hornik, K. and Parmigiani, G. (2008). Applied Spatial Data Analysis with R. ISBN 978-0-387-78170-9 e-ISBN 978-0-387- 78171-6 DOI 10.1007/978-0-387-78171-6. Thomas N O Achia (2010). Environment, Spatial statistics and GIS Notes.