Getting a Map with Points, Using Ggmap and Ggplot2

Getting a map with points, using ggmap and ggplot2

Your longitude and latitude values in geom_point() are in wrong order. lon should be as x values and lat as y values.

 p + geom_point(data=d, aes(x=lon, y=lat),size=5)

Plotting lines over maps in R with ggplot2/ggmap

Since there is no reproducible data, I created a random data. Please provide your data from next time. This is a necessary thing for all SO users when they ask some help.

What you need is to create a data frame for geom_segment. You do not have to loop through the data at all. Each row of of mydf is a line. You specify two points for longitude and latitude, respectively using x, y, xend and yend.

library(ggmap)
library(ggplot2)

# Create a data frame for segments.
mydf <- data.frame(id = 1:3, 
                   lat_1 = c(37.78, 37.75, 37.73), 
                   lon_1 = c(-122.41, -122.40, -122.405), 
                   lat_2 = c(37.77, 37.75, 37.72), 
                   lon_2 = c(-122.43, -122.42, -122.415))

# Create randam data points.
set.seed(111)

mydf2 <- data.frame(lon = runif(n = 100, min = -122.49, max = -122.38),
                    lat = runif(n = 100, min = 37.69, max = 37.813))

# Get a map 
map <- get_map(location = c(left = -122.523, bottom = 37.69,
                            right = -122.35, top = 37.8),
               maptype = "roadmap", source = "google", color = "bw")

# Plot the points and draw the segments on the map. 
ggmap(map) + 
geom_point(data = mydf2, 
           aes(x = lon, y = lat), color = "red", alpha = 0.6, size = 2) + 
geom_segment(data = mydf, 
             aes(x = lon_1, y = lat_1, xend = lon_2, yend = lat_2), 
             color = "green", size = 2, alpha = 0.8, lineend = "round")
#> Warning: Removed 34 rows containing missing values (geom_point).

Created on 2018-03-25 by the reprex package (v0.2.0).

Adding coordinates as points to a map in R

You need to reproject these points, then you can use standard geom_point and geom_text. Your points are far too close together to see them all separately on a world map though:

df <-  sf::sf_project("+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0", 
                      "+proj=moll", df) %>%
       as.data.frame() %>%
      setNames(c("long", "lat")) %>%
      cbind(object = object)

world %>% 
  st_transform(crs = "+proj=moll") %>%
  ggplot() + 
  geom_sf() + 
  theme_minimal() +
  geom_point(data = df, aes(long, lat)) +
  geom_text(data = df, aes(long, lat, label = object),
            vjust = c(1, 0, -1), hjust = 1)

If you zoom it, it is much clearer:

world %>% 
  st_transform(crs = "+proj=moll") %>%
  ggplot() + 
  geom_sf() + 
  theme_minimal() +
  geom_point(data = df, aes(long, lat)) +
  geom_text(data = df, aes(long, lat, label = object),
            vjust = c(0.5, 1, -1), hjust = 1.2) +
  coord_sf(ylim = c(4200000, 4700000), xlim = c(-10.75, -10.25) * 10^6)

using ggmap to plot points randomly distributed within boundaries of shape file

Ok, I sorted it out. The solution is in spsample() in package "raster".

d<-data.frame(id=NA,x=NA,y=NA)
l<-data.frame(id=154,n=10)

for (i in unique(l$id)){
 temp<-spsample(kommune[which(kommune$OBJECTID==i),],n=l[l$id==i,"n"],type="random")
 temp<-as.data.frame(temp)
 temp$id<-i
 d<-rbind(d,temp[,c("id","x","y")])
}
d<-d[-1,] #drop the first empty row

ggmap(map, extent = "normal", maprange = T)+
  geom_polygon(data = dat,
           aes(long, lat, group = group),
           fill = "blue", colour = "yellow", alpha = 0.1)+
  geom_point(aes(x = x, y = y), data = d[which(d$id==154),], alpha = .9,show.legend = T)

Producing a map for each location row using ggmap

We can loop through the data frame to produce one map per row:

library(ggmap)

p <- vector("list", 3)

for (i in seq_along(df)){
  p[[i]] <- ggmap(get_map(location = c(lon = df$lon[i], lat = df$lat[i]), 
                     zoom = 12, color = "bw", source = "google")) +
    geom_point(data=df[i,], aes(x=long, y=lat), color='red')
}

> p[[1]]

> p[[2]]

> p[[3]]

Notes:

1. You had zoom = 12, ... source = "osm" inside the location = c(...) argument. These should be arguments for get_map().
2. For some reason I got an error with openstreetmap (HTTP status was '400 Bad Request'), so I used the default google maps instead.

Improving a location visibility using ggmap function in R

Finding the map by address is convenient, but there is more control if you use the longitude/latitude

map <- get_map(location = c(mean(d$lon), mean(d$lat)), zoom = 13, maptype = "satellite", source = "google")

ggmap(map)+
  geom_point(data = d, aes(x = lon, y = lat))+
  geom_path(data = d, aes(x = lon, y = lat))

ggmap has already set the x and y scales, so you will get warnings if you try to replace them.

---

Related Topics