Customize tm_compass() background

Question

In the code below, how do I set background color and transparency fortm_compass()as I can do for map title?

library(tmap)
library(dismo)

ny.map <- gmap(x = "New York", zoom = 13, type = "satellite")

print(tm_shape(shp = ny.map) +
      tm_raster() +
      tm_compass(position = c("right", "top"),
                 type = "4star",
                 show.labels = 2) +
      tm_layout(title = "New York",
                title.bg.color = "white",
                title.bg.alpha = 0.5))

Thanks

score 3 · Accepted Answer · answered Feb 02 '18 at 16:34

Seeing the CRAN manual, I thought it would not be possible to do the job. My workaround was to manually create a polygon that covers the compass. This is a tedious work, but this is perhaps the way to go right now. The first step is to create a polygon. extent() gives you min and max for longitude and latitude. I used xmax and ymax to specify five points for a polygon. (I played with values and found the optimal values.) We need to assign a right projection to the polygon. If you type ny.map in your R Console, you will see coord. ref.. This is the projection you need. Then, I added the polygon to the map using tm_shape() and tm_fill().

lon <- c(extent(ny.map)[2]-2100, extent(ny.map)[2]-250, extent(ny.map)[2]-250, extent(ny.map)[2]-2100, extent(ny.map)[2]-2100)
lat <- c(extent(ny.map)[4]-250, extent(ny.map)[4]-250, extent(ny.map)[4]-2100, extent(ny.map)[4]-2100,extent(ny.map)[4]-250)

foo <- SpatialPolygons(list(Polygons(list(Polygon(cbind(lon, lat))), ID = 1)),
                   proj4string = CRS("+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs"))

tm_shape(shp = ny.map) +
tm_raster() +
tm_shape(shp = foo) +
tm_fill("red", alpha = 0.4) +
tm_compass(position = c("right", "top"),
           type = "4star",
           show.labels = 2) +
tm_layout(title = "New York",
          title.bg.color = "white",
          title.bg.alpha = 0.5)

I too couldn't find a way to do this easily; for example,`tm_text()`takes arguments`bg.color`and`bg.alpha`and wish`tm_compass()`had something similar. Your method works for the time being. Thanks. — Manojit, Feb 03 '18 at 02:20
@Manojit I see. Let's hope there will be an update in the package. If your case is done, please click the green tick below the voting triangles. In this way, future SO reader will know that the solution is working. — jazzurro, Feb 03 '18 at 02:24

score 1 · Answer 2 · answered Jul 29 '20 at 15:24

Customizing tm_compass() (and tm_scale_bar()) background is supported starting from tmap version 3.1:

library(spData)
library(tmap)

tm_shape(elev) +
  tm_raster() + 
  tm_compass(bg.color = "white", 
             bg.alpha = 0.7,
             type = "8star",
             position = c("left", "bottom"),
             size = 3) +
  tm_layout(legend.show = FALSE)

Customize tm_compass() background

2 Answers2