CODEWITHSUNDEEP
rcountpolygonshapefilepoint-in-polygon
James Todd
James Todd

Reputation: 123

Counting points within each LSOA(polygon)

I am attempting to count the number of points within each LSOA area within London. I have attempted to use the over function although the output does not produce a count of the number of listings per LSOA

The code I have conducted so far is as follows 

ldnLSOA <- readOGR(".", "LSOA_2011_London_gen_MHW")
LondonListings <- read.csv('Londonlistings.csv') 
proj4string(LdnLSOA) <- proj4string(LondonListings) 
plot(ldnLSOA) 
plot(LondonListings, add =T)

enter image description here

LSOAcounts <- over(LondonListings, ldnLSOA)

This produces a table with no additional data than the original ldnLSOA shapefile.

I was wondering if someone knew how I would be able to get a table in the format: 

LSOAname | LSOAcode | Count

or that sort of framework.

Example data: 

LondonListings: 
longitude | latituide 
-0.204406 51.52060
-0.034617 51.45037
-0.221920 51.46449
-0.126562 51.47158
-0.188879 51.57068
-0.096917 51.49281

Shapefile:

https://data.london.gov.uk/dataset/statistical-gis-boundary-files-london

Upvotes: 0

Views: 888

Answers (1)

Thai
Thai

Reputation: 513

I deleted my inespecific answer and wrote another one with your data (except for the points... but it is not hard to replace this data, right?) Let me know if it worked!

#I'm not sure which of this libs are used, since I always have all of them loaded here
library(rgeos)
library(rgdal)
library(sp)


#Load the shapefile
ldnLSOA <- readOGR(".", "LSOA_2011_London_gen_MHW")
plot(ldnLSOA)

#It's always good to take a look in the data associated to your map
ldn_data<-as.data.frame(ldnLSOA@data)

#Create some random point in this shapefile
ldn_points<-spsample(ldnLSOA,n=1000, type="random")

plot(ldnLSOA)
plot(ldn_points, pch=21, cex=0.5, col="red", add=TRUE)

#create an empty df with as many rows as polygons in the shapefile
df<-as.data.frame(matrix(ncol=3, nrow=length(ldnLSOA@data$LSOA11NM)))
colnames(df)<- c("LSOA_name","LSOA_code", "pt_Count")
df$LSOAname<-ldn_data$LSOA11NM
df$LSOAcode<-ldn_data$LSOA11CD

# Over = at the spatial locations of object x,
# retrieves the indexes or attributes from spatial object y
pt.poly <- over(ldn_points,ldnLSOA)

# Now let's count
pt.count<-as.data.frame(table(pt.poly$LSOA11CD))

#As it came in alphabetical order, let's put in the same order of data in data frame  
pt.count_ord<-as.data.frame(pt.count[match(df$LSOA_name,pt.count$Var1),])

#Fill 3rd col with counts
df[,3]<-pt.count_ord$Freq

Upvotes: 1

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