CODEWITHSUNDEEP
rmapsshapesspatial
iouraich
iouraich

Reputation: 3034

How to convert .shp file into .csv in R?

I want to to convert two .shp files into one database that would allow me to draw the maps together.

Also, is there a way to convert .shp files into .csv files? I want to be able to personalize and add some data which is easier for me under a .csv format. What I have in mind if to add overlay yield data and precipitation data on the maps.

Here are the shapefiles for Morocco, and Western Sahara.

Code to plot the two files:

# This is code for mapping of CGE_Morocco results

# Loading administrative coordinates for Morocco maps
library(sp)
library(maptools)
library(mapdata)

# Loading shape files
Mor <- readShapeSpatial("F:/Purdue University/RA_Position/PhD_ResearchandDissert/PhD_Draft/Country-CGE/MAR_adm1.shp")
Sah <- readShapeSpatial("F:/Purdue University/RA_Position/PhD_ResearchandDissert/PhD_Draft/Country-CGE/ESH_adm1.shp")

# Ploting the maps (raw)
png("Morocco.png")
Morocco <- readShapePoly("F:/Purdue University/RA_Position/PhD_ResearchandDissert/PhD_Draft/Country-CGE/MAR_adm1.shp")
plot(Morocco)
dev.off()

png("WesternSahara.png")
WesternSahara <- readShapePoly("F:/Purdue University/RA_Position/PhD_ResearchandDissert/PhD_Draft/Country-CGE/ESH_adm1.shp")
plot(WesternSahara)
dev.off()

Morocco WesternSahara

After looking into suggestions from @AriBFriedman and @PaulHiemstra and subsequently figuring out how to merge .shp files, I have managed to produce the following map using the following code and data (For .shp data, cf. links above)

code:

# Merging Mor and Sah .shp files into one .shp file

MoroccoData <- rbind(Mor@data,Sah@data) # First, 'stack' the attribute list rows using rbind() 
MoroccoPolys <- c(Mor@polygons,Sah@polygons) # Next, combine the two polygon lists into a single list using c()

summary(MoroccoData)
summary(MoroccoPolys)

offset <- length(MoroccoPolys) # Next, generate a new polygon ID for the new SpatialPolygonDataFrame object

browser()
for (i in 1: offset)
{
sNew =  as.character(i)
MoroccoPolys[[i]]@ID = sNew
}

ID <- c(as.character(1:length(MoroccoPolys))) # Create an identical ID field and append it to the merged Data component
MoroccoDataWithID <- cbind(ID,MoroccoData)

MoroccoPolysSP <- SpatialPolygons(MoroccoPolys,proj4string=CRS(proj4string(Sah))) #  Promote the merged list to a SpatialPolygons data object

Morocco <- SpatialPolygonsDataFrame(MoroccoPolysSP,data = MoroccoDataWithID,match.ID = FALSE) #  Combine the merged Data and Polygon components into a new SpatialPolygonsDataFrame.

Morocco@data$id <- rownames(Morocco@data)
Morocco.fort <- fortify(Morocco, region='id') 
Morocco.fort <- Morocco.fort[order(Morocco.fort$order), ] 

MoroccoMap <- ggplot(data=Morocco.fort, aes(long, lat, group=group)) + 
geom_polygon(colour='black',fill='white') + 
theme_bw()

Results:

MoroccoMAp

New Question:

1- How to eliminate the boundaries data that cuts though the map in half?

2- How to combine different regions within a .shp file?

Thanks you all.

P.S: the community in stackoverflow.com is wonderful and very helpful, and especially toward beginners like :) Just thought of emphasizing it.

Upvotes: 2

Views: 13198

Answers (2)

Paul Hiemstra
Paul Hiemstra

Reputation: 60924

Once you have loaded your shapefiles into Spatial{Lines/Polygons}DataFrames (classes from the sp-package), you can use the fortify generic function to transform them to flat data.frame format. The specific functions for the fortify generic are included in the ggplot2 package, so you'll need to load that first. A code example:

library(ggplot2)
polygon_dataframe = fortify(polygon_spdf)

where polygon_spdf is a SpatialPolygonsDataFrame. A similar approach works for SpatialLinesDataFrame's.

The difference between my solution and that of @AriBFriedman is that mine includes the x and y coordinates of the polygons/lines, in addition to the data associated to those polgons/lines. I really like visualising my spatial data with the ggplot2 package.

Once you have your data in a normal data.frame you can simply use write.csv to generate a csv file on disk.

Upvotes: 8

Ari B. Friedman
Ari B. Friedman

Reputation: 72731

I think you mean you want the associated data.frame from each?

If so, it can be accessed with the @ slot access function. The slot is called data:

write.csv( WesternSahara@data, file="/home/wherever/myWesternSahara.csv")

Then when you read it back in with read.csv, you can try assigning:

myEdits <- read.csv("/home/wherever/myWesternSahara_modified.csv")
WesternSahara@data <- myEdits

You may need to do some massaging of row names and so forth to get it to accept the new data.frame as valid. I'd probably try to merge the existing data.frame with a csv you read in in R, rather than making edits destructively....

Upvotes: 6

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