如何为facet_wrap面板实现不同的缩放级别？

Question

我想为一个facet_wrap面板设置不同的缩放级别。我该如何实现？

p <- ggmap(get_googlemap(center = c(lon = 14.444, lat = 50.015),
                         zoom = 4, scale = 2))
p +  geom_point(data = some_data, aes(x = long, y = lat, color = some_variable)) +
     facet_wrap(~ some_variable)