Bind polygon centroid to polygon attribute data

Question

I am trying to bind a dataframe containing polygon centroids to the polygon attributes.

Here's what I've done so far to create the centroids:

library(rgdal)
library(PBSmapping)
library(maptools)
library(sp)

gisCentroids<-coordinates(gisPolygons)

I am wanting to combine the resultant centroids to the attribute data from gisPolygons. How do I go about achieving this? I have tried over from sp package but it does not seem to work giving me error messages. The code used is shown below:

ID<-over(SpatialPoints(gisCentroids),gisPolygons)
CentroidPolys<-cbind(gisCentroids,gisPolygons)

I want to do further intersection and overlap analyses once I have the centroids information bound to the polygon attributes.

Any suggestions?

Answer 1

Load libraries and example data

# Load libraries
library('raster')
library('geosphere')
library('mapview') # incredible interactive map visualization in R

# Get SpatialPolygonsDataFrame object example
polygons <- getData('GADM', country = 'URY', level = 1)

Plot example data

# Plot Polygons
mapview(polygons)

# Get polygons centroids
centroids <- as.data.frame(centroid(polygons))
colnames(centroids) <- c("lon", "lat") 
centroids <- data.frame("ID" = 1:nrow(centroids), centroids)

# Create SpatialPointsDataFrame object
coordinates(centroids) <- c("lon", "lat") 
proj4string(centroids) <- proj4string(polygons) # assign projection

Plot polygons + centroids

# Plot Polygons + Centroids
mapview(polygons) + mapview(centroids)

Getting attributes

# Get polygons attribute for each centroid point 
centroids@data <- sp::over(x = centroids, y = polygons, returnList = FALSE)

#class       : SpatialPointsDataFrame 
#features    : 19 
#extent      : -57.76437, -54.02354, -34.82602, -30.54739  (xmin, xmax, ymin, ymax)
#coord. ref. : +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0 
#variables   : 13
#names       : OBJECTID, ID_0, ISO,  NAME_0, ID_1,         NAME_1, HASC_1, CCN_1, CCA_1,       TYPE_1,  ENGTYPE_1, NL_NAME_1,  VARNAME_1 
#min values  :        1,  245, URY, Uruguay,    1,        Artigas,  UY.AR,    NA,      , Departamento, Department,          ,            
#max values  :       19,  245, URY, Uruguay,   19, Treinta y Tres,  UY.TT,    NA,      , Departamento, Department,          , Montevidéu 

Final plot

# Plot centroids with data (click on point to see the information)
mapview(centroids)