How keep information from shapefile after fortify()

Question

How can I keep polygons\'s information after shapefile? Let me try to explain:

I have a shapefile with this data:

> head(mapa@data)
         ID      C         


        

Answer 1

Assumption that data$CD_GEOCODI and shape@data are both unique for each row. Below is a better and simpler answer:

library(dplyr)
library(ggplot2)

# fortify the shape file
  map.df <- fortify(shape, region ="CD_GEOCODI")

# change data$CD_GEOCODI to character, as shp.df$CD_GEOCODI is of character class.
  data <- data %>% mutate(data, CD_GEOCODI = as.character(CD_GEOCODI))

# merge data
  map.df <- left_join(map.df, data, by=c('id'='CD_GEOCODI'))

Answer 2

Since you did not provide your shapefile or data, it's impossible to test, but something like this should work:

# not tested...
library(plyr)      # for join(...)
library(rgdal)     # for readOGR(...)
library(ggplot2)   # for fortify(...)

mapa <- readOGR(dsn=".",layer="shapefile name w/o .shp extension")
map@data$id <- rownames(mapa@data)
mapa@data   <- join(mapa@data, data, by="CD_GEOCODI")
mapa.df     <- fortify(mapa)
mapa.df     <- join(mapa.df,mapa@data, by="id")

ggplot(mapa.df, aes(x=long, y=lat, group=group))+
  geom_polygon(aes(fill=Population))+
  coord_fixed()

Answer 3

Maybe this is a slightly simpler solution

library(dplyr)
library(ggplot2)

# fortify the shape file
  map.df <- fortify(shape, region ="CD_GEOCODI")

# merge data
  map.df <- left_join(map.df, data, by=c('id'='CD_GEOCODI'))

Answer 4

I came across the same problem and was able to achieve the desired results using slightly different approach.

Import and fortify

I have used the following code to read the shapes:

shps <- maptools::readShapePoly(fn = file.path("file",
                                               "path",
                                               "no extension"),
                                     # Column with unique IDs
                                     IDvar = "geoID")

and subsequently fortified the objet using the code:

shpsFort <- ggplot2::fortify(model = shps)

Results

This created a data.frame object with the id value corresponding to the column passed in IDvar = "geoID". Adding any other data could be simply addressed via ordinary merge command.