Recently some code I've been using to make facet maps has started to give me this warning message
Warning message:
Unknown or uninitialised column: 'region'.
The map file I have created, called worldMap, has the following columns
"long" "lat" "order" "hole" "piece" "group" "id"
And the data source has the following columns
"scenario" "id" "value"
The code that generates the error is
gg <- ggplot(data = d, aes(map_id = id))
gg <- gg + geom_map(aes(fill = value), map = worldMap)
If I add a new column to the map that has the value of id like this
worldMap$region <- worldMap$id
the warning message disappears. But why do I need to do this? The help text for the map option of geom_map says
It must contain columns x or long, y or lat, and region or id.
The code in geom_map that seems relevant is
stopifnot(is.data.frame(map))
if (!is.null(map$lat))
map$y <- map$lat
if (!is.null(map$long))
map$x <- map$long
if (!is.null(map$region))
map$id <- map$region
Anyway, I can solve my problem by just adding the column "region" but that seems like a kludge.
