Map_data() documentation has what seems like a typo

[ericopatto]

This is not a complicated problem. In the reference page for the function map_data() (here), the example has the following call:

ggplot(choro, aes(long, lat)) +
  geom_polygon(aes(group = group, fill = assault)) +
  coord_map("albers",  at0 = 45.5, lat1 = 29.5)
}

And then later, there is something slightly different.

However, the call coord_map() should have lat0 instead of at0 as an argument (in both examples):

ggplot(choro, aes(long, lat)) +
  geom_polygon(aes(group = group, fill = assault)) +
  coord_map("albers",  lat0 = 45.5, lat1 = 29.5)
}

It works either way, since the name doesn't seem to matter here, but it's rather confusing.

I hope I'm doing this right. I've never used GitHub before, so maybe I'm wrong about something (maybe I'm filing it in the wrong place)... I just think this should be pointed out somewhere.

[yutannihilation]

Good catch. I too think it's a typo, but it seems it doesn't matter what names we use. These arguments are passed to parameters argument of mapproj::mapproject(), and then converted as a double vector.

https://github.com/cran/mapproj/blob/1307e2c77a8bfa3e41ffe7eee773b487fdc7a195/R/mapproj.r#L46

I don't check the source of the C code, but probably it doesn't use the names, as the example shows unnamed forms:

map("state",proj="albers",par=c(30,40))

A pull request to fix this is welcome, but I would also note that we are moving away from coord_map(). (c.f. #3721)