R中的多边形贴图（空间数据）

Question

Could someone help me create a polygon map according to the real estate dataset( https://docs.google.com/spreadsheets/d/1g_awI6hnD80IVeZDOWpvU_NHdHxsk_Uyo8HML9p-yHo/edit#gid=0 )? I want to get a regional map of Sacramento with different colors representing different real estate prices.

The code that I provided below came from a sample polygon R code. I can't figure out how the "merge" function works in polygon maps.

Thank you,

#load libraries
library(ggmap)
library(ggplot2) 
library(gpclib)
library(rgeos)


getClass("Polygon")
getClass("SpatialPolygons")
realestate.f <- fortify(realestate, region = "zip")
realestate.f <- merge(realestate.f, realestate, by.x = "longitude", by.y = "latitude")
head(realestate.f)

Map <- ggplot(realestate.f, aes(longitude, latitude, price)) + 
geom_polygon() + coord_equal() + 
labs(x = "longitude", y = "latitude", "price") + 
ggtitle("Sacramento Real Estate Prices")

Map + scale_fill_gradient(low = "white", high = "black")`

Answer 1

@Yun Zhou: it looks like you are starting with point data. I believe you first need to convert your dataframe to a SpatialPointsDataFrame before you can convert the points to polygonal data (or some density function).

#dataframe from csv
df.in

# Coerce to SpatialPointsDataFrame
coordinates(df.in) = c("latitude", "longitude") 
class(df.in) #it should be a sptial points data frame
plot(df.in)

Plot: