implement plotting for multiline/polygon objects

[mpadge]

This doesn't actually work at all!

[MathieuMarauri]

Hello Mark,

I attended yout talk in the useR2017 conference, it was great. I wanted to give your package a try and I encountered an error I can't seem to solve.

I tried to plot natural parks on a map with add_osm_objects and it gave an error. Natural parks are multipolygons, is this the same thing as this issue ?

My code is below

tignes_box <- get_bbox (c(6.88, 45.45, 6.92, 45.48))
tignes_parks <- extract_osm_objects(key = 'boundary',
                                    value = 'national_park',
                                    bbox = tignes_box)
tignes_map <- osm_basemap(bbox = tignes_box, bg = 'gray80')
tignes_map <- add_osm_objects(obj = tignes_parks, col = 'forestgreen')

The error is Error in geom_to_xy(obj, obj_type) : object 'xy' not found.

Anyway thank you for this great package.

Mathieu

[mpadge]

thanks a lot @MathieuMarauri! What you want should now be implemented:

tignes_box <- get_bbox (c(6.6, 45.1, 7.0, 45.6))
tignes_parks <- extract_osm_objects(key = 'boundary', value = 'national_park',
    bbox = tignes_box)
tignes_map <- osm_basemap(bbox = tignes_box, bg = 'gray80')
tignes_map <- add_osm_objects(tignes_map, obj = tignes_parks, col = 'forestgreen')
print_osm_map (tignes_map)

(Note that I adjusted your bounding box a little - this map actually contains two adjacent multipolygons.)

---

Note also that these are only "multipolygons" because that's an OSM rule for boundaries, but they're not really geometrical multipolygons because they have no "inner" and "outer" objects. A more complex example is islands within rivers (in this case one called Chiswick Eyot):

bb <- get_bbox (c(-0.25, 51.48, -0.235, 51.49))                                     
obj <- extract_osm_objects(bbox = bb, key = 'name', value = 'River Thames',
                           return_type = "multipolygon")
map <- osm_basemap(bbox = bb, bg = 'gray80') %>%
    add_osm_objects (obj = obj, col = "skyblue")
print_osm_map (map)

Now just have to do same for multiline objects ...

[MathieuMarauri]

Hello Mark,

Thanks a lot for your quick answer. It works perfectly.

Have a nice day,

Mathieu

[beemyfriend]

I had a similar problem

trial <- get_bbox(c(-75.1, 39.9, -75.2, 40))
dat_H <- extract_osm_objects(key = 'highway', bbox = trial)
dat_W <- extract_osm_objects(key = 'waterway', bbox = trial)
dat_W <- extract_osm_objects(key = 'waterway',  bbox = trial)

osm_basemap(trial, bg = 'gray80') %>%
  add_osm_objects(dat_H) %>%
  add_osm_objects(dat_W,
                  'blue') %>%
  print_osm_map()

the extract_osm_objects() was returning multipolygons, I ended up forcing them into normal polygons by typing:

dat_W <- extract_osm_objects(key = 'waterway',  bbox = trial, return_type = 'polygon')

I don't actually understand the problem. I just guessed and it ended up working. Why are multipolygons/multilines giving osmplotr a hard time? What can I do to help?

[mpadge]

That example actually works as intended at the moment - most NYC Philly waterways are simply polygons only with no multipolygons, which is why the force is needed. I guess I could or should implement more informative messages, so rather than just No valid data returned it would say something like, defaulting to multipolygons ... no valid data; maybe try return_type = "polygons"? The place to implement that would be somewhere in these lines - feel free to PR!

(This issue is open because multilines are still awaiting proper implementation.)