[Spanish version|Ejemplo de integración de esDBpedia con API de localidata]

[Localidata |http://www.localidata.com] is a Spanish company that provides [an API|https://localidata.3scale.net/] to access their semantic data. We can request information about business premises, district geometries and many more.

In order to use this API you have to use a api_key that you get when you register.

With this example in R you can get from Localidata the contour segments of the Justicia district (in Madrid) and, following  [the first example|ejemplos de uso de los datos esDBpedia], display the locations known by esDBpedia.

%%prettify
{{{
library(httr)
library(jsonlite)
library(ggmap)
library(SPARQL)
#Example without pagination
#Info about the Justicia district (code 280796014)
res <- GET("http://datos.localidata.com",
            path = "recurso/territorio/Barrio/280796014.geojson",
            query = list(
                         api_key = "YOU_API_KEY",
                         `_view` = "coordenadas" #You have to escape variables starting with _
                        )                        
          )

json <- fromJSON(rawToChar(res$content)) #The json sent by the server

#You have the polyline with the district frontiers in 
#json$features$geometry$coordinates[[1]][[1]][[1]][[N]] 
#N coordinates. There are 359 segments.
v_lat <- numeric(length(json$features$geometry$coordinates[[1]][[1]][[1]]))
v_lon <- numeric(length(json$features$geometry$coordinates[[1]][[1]][[1]]))
for (i in 1:length(v_lat)){
  v_lon[i] <- json$features$geometry$coordinates[[1]][[1]][[1]][[i]][1]
  v_lat[i] <- json$features$geometry$coordinates[[1]][[1]][[1]][[i]][2]
}
dfpoli <- data.frame(lat=v_lat, lon=v_lon) #long should NOT change its sign

#Google Map with the district borders
map.center <- geocode("Chueca, Madrid, Spain")
map <- get_map(c(lon=map.center$lon, lat=map.center$lat),
                 source="google", zoom=15)
plot <- ggmap(map) +
  geom_polygon(aes(lon, lat), data = dfpoli, colour = NA, fill = "red", alpha = .3)

#Add esDBpedia geographical data to the map
endpoint <- "http://es.dbpedia.org/sparql"
query <- 
"SELECT *  WHERE {
      ?uri geo:lat ?lat .
      ?uri geo:long ?lon .
      ?uri rdf:type ?thetype .
      FILTER ( (?lat> 40.418  && ?lat < 40.430) &&
               (?lon> -3.704  && ?lon <-3.690)
               && regex(?thetype,'^http://schema.org')
             )
}
"
reslist <- SPARQL(endpoint,query)
df <- reslist$results
df$thetype <- factor(df$thetype)
plot + geom_point(data=df,  
                        aes(x=lon, y=lat, colour=thetype, position="dodge"),
                        size=6, alpha=0.8
                        )

          
}}}
%%

This is the result
[{Image src='justicia.png' align='left'}]