plotting shape file in ggplot2

Question

I'm trying to figure out how to display my complete map in gglot2 including the island Both r_base and tmap were able to display the islands but ggplot2 couldn't differentiate the island from the rest of the waterbody... .

My question is how to make the Islands appear in ggplot2?

See the code i used below.

library(ggplot2)
library (rgdal)
library (rgeos)
library(maptools)
library(tmap)

Loading the Persian Gulf shape fill referred to as iho

PG <- readShapePoly("iho.shp")

the shape file is available here

http://geo.vliz.be:80/geoserver/wfs?request=getfeature&service=wfs&version=1.0.0&typename=MarineRegions:iho&outputformat=SHAPE-ZIP&filter=%3CPropertyIsEqualTo%3E%3CPropertyName%3Eid%3C%2FPropertyName%3E%3CLiteral%3E41%3C%2FLiteral%3E%3C%2FPropertyIsEqualTo%3E

plot with r_base

Q<-plot(PG)

Corresponds to figure A

Ploting with tmap

qtm(PG)

Corresponds to figure B

convert to dataframe

AG <- fortify(PG)

Plot with ggplot2

ggplot()+ geom_polygon(data=AG, aes(long, lat, group = group), colour = alpha("darkred", 1/2), size = 0.7, fill = 'skyblue', alpha = .3)

Corresponds to figure C

Answer 1

You need to tell ggplot you want the holes filled in with a different color..for example:

ggplot()+ geom_polygon(data=AG, aes(long, lat, group = group, fill = hole), colour = alpha("darkred", 1/2), size = 0.7) + scale_fill_manual(values = c("skyblue", "white")) + theme(legend.position="none")

Also try readOGR() function from the rgdal package instead of readShapePoly() it keeps all the projection and datum information when you read the shape file.