Filled Polygons using ggplot in R not working

Question

The following code works well for drawing polygons

SP <- SpatialPolygons(spd)
centroids  <- coordinates(SP)
x  <- centroids[,1]
y  <- centroids[,2]
SP1  <- SpatialPolygonsDataFrame(SP, data = data.frame(x = x, y = y, z = z, row.names = row.names(SP)))
ggplot(data = SP1, aes(x = long, y = lat, group = group)) + geom_path()

Instead if I change the last two lines of the code to fill these polygons based on some value vector it does not work:

penetration <- runif(n = length(SP), min = 1, max = 10)
SP1  <- SpatialPolygonsDataFrame(SP, data = data.frame(x = x, y = y, z = z,  value = penetration, row.names = row.names(SP)))
ggplot(data = SP1, aes(x = long, y = lat, group = group)) + geom_polygon(aes(fill=SP1$value))

spd is created with data from the following link:

data source: https://www.google.com/maps/d/viewer?mid=1mf9TQY3bocarO4SaIXAtco_C1LE&hl=en_US

I then extracted coordinates from the kml file... which is then into a list of Polygons so that I could draw it using some plotting function...

tkml <- getKMLcoordinates(kmlfile="Pune all Electoral Wards.kml", ignoreAltitude=T)
len <-length(tkml)

del <- NA
for(i in 1:len)
{
  if(length(tkml[[i]]) == 2)
    del <- c(del, i)
}
del <- del[-1]
tkmlCleaned <- tkml[!tkml %in% tkml[del]]
size <- length(tkmlCleaned)
sr <- vector(mode = "list", length = size)
srs <- vector(mode = "list", length = size)
spd <- list()
for(j in 1:length(sr))
{

  sr[[j]] <- Polygon(tkmlCleaned[[j]])
  srs[[j]] <- Polygons(list(sr[[j]]), j)
  spd <- c(srs[[j]], spd)
}

Answer 1

There's a lot more to this, it's interestingly painful in a couple of places. There are easier steps in some ways with less base ggplot2 functions, but I'm not used to them yet.

Maybe this will help you . . .

library(rgdal);

## we can only read one layer at a time, to see which layers are there run
##ogrListLayers("Pune all Electoral Wards.kml")
#"Pune Prabhags 2012 onwards"
#"PMC Adminstrative Ward Offices"

spd <- readOGR("Pune all Electoral Wards.kml", "PMC Adminstrative Ward Offices")

library(ggplot2)

## this is the table of all coordinates, classified by object and part-of-object
spdtab <- fortify(spd)

## but note that we don't have any of the layer-attributes
head(spdtab)

## to put them on we can use merge(), but it's much easier with dplyr IMO
library(dplyr)
gislayerdata <- mutate(as.data.frame(spd), id = as.character(row_number()))
spdtab <- inner_join(spdtab, gislayerdata, "id")

ggplot(spdtab) + aes(x = long, y = lat, group = group, fill = Name) + 
   geom_polygon() + 
   guides(fill = FALSE) 

Answer 2

you don't mention which error it yields, but, for these cases,

aes(x=long, y=lat, group=group, fill=group)

has worked for me