[R-sig-Geo] Calculate each polygon percentage inside a circles

[ASANTOS]

Dear members,

        I will try to calculate each polygon percentage inside a circles 
given an arbitrary radius in a shapefile object with the code below and 
my output needs to be (Two first columns with center os circle 
coordinates and values of each polygon percentage):

"pts$x"   "pts$y" "ID1" "ID2" "ID3" "ID4"
180486.1  330358.8  16.3   0.2  NA   17.3
179884.4  331420.8  88.3   NA   96.3 NA
179799.6  333062.5  25.3   22.3 0.5  NA
...

      For this I try to do:

#Packages
require(shapefiles)
require(rgdal)
require(maptools)
require(spatstat)
require(berryFunctions)


#Create 4 polygons (I create polygons because is more simple that given 
a shapefile in a post)

sr1=Polygons(list(Polygon(cbind(c(180114, 180553, 181127, 181477, 
181294, 181007, 180409,
   180162, 180114), c(332349, 332057, 332342, 333250, 333558, 333676,
   332618, 332413, 332349)))),'1')
sr2=Polygons(list(Polygon(cbind(c(180042, 180545, 180553, 180314, 
179955, 179142, 179437,
   179524, 179979, 180042), c(332373, 332026, 331426, 330889, 330683,
   331133, 331623, 332152, 332357, 332373)))),'2')
sr3=Polygons(list(Polygon(cbind(c(179110, 179907, 180433, 180712, 
180752, 180329, 179875,
   179668, 179572, 179269, 178879, 178600, 178544, 179046, 179110),
   c(331086, 330620, 330494, 330265, 330075, 330233, 330336, 330004,
   329783, 329665, 329720, 329933, 330478, 331062, 331086)))),'3')
sr4=Polygons(list(Polygon(cbind(c(180304, 180403,179632,179420,180304),
   c(332791, 333204, 333635, 333058, 332791)))),'4')

#Spatial Polygons
sr=SpatialPolygons(list(sr1,sr2,sr3,sr4))
srdf=SpatialPolygonsDataFrame(sr, 
data.frame(row.names=c('1','2','3','4'), PIDS=1:4))

#Create shapefile
writeOGR(srdf, getwd(), 'POLY', 'ESRI Shapefile')

#Read shapefile
contorno_line_X <- readShapeSpatial("POLY.shp")
plot(contorno_line_X)

#Create ~28 random points in my window
contorno_line_spat <- as(contorno_line_X,"owin")
pts <- rpoispp(lambda=0.000005, win=contorno_line_spat)
points(pts, col="blue")

#Set the radius for the plots
radius <- 600  # radius in meters

#Draw the circles using berryFunctions package
for(i in 1:length(pts$x)) circle(pts$x[i],pts$y[i],r=radius, 
col=rgb(1,0.5,0,alpha=0.4), border=NA)
#

Now I'd like to calculate de polygon percentage around each point in a 
600 meters radius. This is possible? There are any function for this?

Thanks,

Alexandre

-- 
======================================================================
Alexandre dos Santos
Proteção Florestal
IFMT - Instituto Federal de Educação, Ciência e Tecnologia de Mato Grosso
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Bairro: Distrito Industrial
Cáceres - MT                      CEP: 78.200-000
Fone: (+55) 65 8132-8112 (TIM)   (+55) 65 9686-6970 (VIVO)

         alexandre.santos at cas.ifmt.edu.br
Lattes: http://lattes.cnpq.br/1360403201088680
OrcID: orcid.org/0000-0001-8232-6722
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