Why do I get 2 legends in ggmap?

[C W]

Dear ggplot2 list,

I am reproducing two ggmap examples from Kahle & Hadley's example, but do not get the same.

In example one, I got two legends instead of one. In example two, overlay() function is not found.

Map and dataset are attached. I guess some arguments have changed since then?

Here's example 1 code:

houston <- get_map("houston", zoom = 14) 

HoustonMap <- ggmap(houston, extent = "device", legend = "topleft")

HoustonMap + stat_density2d(

  aes(x = lon, y = lat, fill = ..level..,

  alpha = ..level..),

  size = 2, bins = 4, data = crime,

  geom = "polygon")

Here's example 2 code (continues from example 1):

overlay <- stat_density2d(

  aes(x = lon, y = lat, fill = ..level..,

      alpha = ..level..),

  bins = 4, geom = "polygon",

  data = violent_crimes)

HoustonMap + overlay + inset(

  grob = ggplotGrob(ggplot() +

                      overlay + theme_inset()),

  xmin = -95.35836, xmax = Inf,

  ymin = -Inf, ymax = 29.75062

)

> Error: object 'overlay' not found

Could someone let me know what I should do in this case? Thank you so much!

Mike