ggspatial::geom_spatial_path() function not working as intended-CodePudding

I'm currently studying the basics of GIS with R at this

But when I use ggplot2 and ggspatial packages, a 4th line is added to speed_limit plot, and I really don't know why.

sp_df <- ggspatial::df_spatial(line_sf)

p1 <- ggplot2::ggplot(sp_df, aes(x,y))  
  ggspatial::geom_spatial_path(aes(colour = road_name))  
  ggspatial::coord_sf(crs = 4326)  
  xlab("lon")  
  ylab("lat")  
  ggtitle("road_name")


p2 <- ggplot2::ggplot(sp_df, aes(x,y))  
  ggspatial::geom_spatial_path(aes(color = speed_limit))  
  ggspatial::coord_sf(crs = 4326)  
  xlab("lon")  
  ylab("lat")  
  ggtitle("speed_limit")

p1 / p2

What's the problem here? Where that additional line comes from? Am I doing something wrong or is this a bug? Any help is appreciated.

CodePudding user response：

You seem to be doing things the hard way, since ggplot has excellent sf support. Rather than loading an extra dependency, using extra code and converting to a data frame, why not simply plot the sf object directly?

p1 <- ggplot(line_sf)  
  geom_sf(aes(geometry = line_sfc, color = road_name))  
  labs(title = "road_name", x = "lon", y = "lat") 

p2 <- ggplot(line_sf)  
  geom_sf(aes(geometry = line_sfc, color = speed_limit))  
  labs(title = "speed_limit", x = "lon", y = "lat")

p1 / p2

If you have good reasons for converting to a data frame, the alternative is to group the second plot by road name so that adjacent groups aren't connected:

sp_df <- ggspatial::df_spatial(line_sf)

p1 <- ggplot2::ggplot(sp_df, aes(x,y))  
  ggspatial::geom_spatial_path(aes(colour = road_name))  
  ggspatial::coord_sf(crs = 4326)  
  xlab("lon")  
  ylab("lat")  
  ggtitle("road_name")

ggplot2::ggplot(sp_df, aes(x,y))  
  ggspatial::geom_spatial_path(aes(color = speed_limit, group = road_name))  
  ggspatial::coord_sf(crs = 4326)  
  xlab("lon")  
  ylab("lat")  
  ggtitle("speed_limit")

p1 / p2