r - Choropleth or Thematic map creation from number of points within Shapefile polygon -
i have geocoded data points (.csv) , shapefile (tigerline) read r , maps overlaying points (locations) on polygons (counties) under same projection using plot() , add=.
i trying find way map number of points found in each polygon (county). assume choropleth or sort of thematic map. associating shapefile , points throwing me loop.
and if can't tell, both r , spatial analysis newbie
i have gotten far:
count1<-table(epoints.spdf$county.name)
count1
count2<-as.data.frame(count1)
count2
county$count<-count2
merge(count2$freq, county$count, = c('var1', 'county.name'))
error in fix.by(by.x, x) : 'by' must specify uniquely valid columns
var1 freq
1 amelia 7
2 caroline 33
3 charles city 1
4 chesterfield 209
5 colonial heights 26
6 dinwiddie 23
7 goochland 15
8 hanover 84
9 henrico 241
10 hopewell 24
11 king william 12
12 new kent 23
13 petersburg 38
14 powhatan 20
15 prince george 18
16 richmond 194
17 sussex 16
solved:
count1<-table(epoints.spdf$county.name)
count1
count2<-as.data.frame(count1)
count2
merge(count2, county@data, by.x = 'var1', by.y= 'name')
names(county)
data.frame(county)
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