When place names are positional aesthetics

Step 00 - mapping data US map

library(tidyverse)

usmapdata::us_map("states") %>% 
  ggplot() +
  aes(geometry = geom) +
  geom_sf() -> p; p

p$coordinates$crs

## NULL

usmapdata::us_map("states")

## Simple feature collection with 51 features and 3 fields
## Geometry type: MULTIPOLYGON
## Dimension:     XY
## Bounding box:  xmin: -2590847 ymin: -2608148 xmax: 2523581 ymax: 731407.9
## Projected CRS: NAD27 / US National Atlas Equal Area
## # A tibble: 51 × 4
##    fips  abbr  full                                                         geom
##    <chr> <chr> <chr>                                          <MULTIPOLYGON [m]>
##  1 02    AK    Alaska               (((-2396847 -2547721, -2393297 -2546391, -2…
##  2 01    AL    Alabama              (((1093777 -1378535, 1093269 -1374223, 1092…
##  3 05    AR    Arkansas             (((483065.2 -927788.2, 506062 -926263.3, 53…
##  4 04    AZ    Arizona              (((-1388676 -1254584, -1389181 -1251856, -1…
##  5 06    CA    California           (((-1719946 -1090033, -1709611 -1090026, -1…
##  6 08    CO    Colorado             (((-789538.7 -678773.8, -789538.2 -678769.5…
##  7 09    CT    Connecticut          (((2161733 -83737.52, 2177182 -65221.22, 21…
##  8 11    DC    District of Columbia (((1955479 -402055.2, 1960234 -393571.9, 19…
##  9 10    DE    Delaware             (((2042506 -284367.3, 2043078 -280000.3, 20…
## 10 12    FL    Florida              (((1855611 -2064809, 1860157 -2054372, 1867…
## # ℹ 41 more rows

Step 0 - a dream

flat_data %>% 
  ggplot() + 
  aes(state_name = state) + 
  geom_state() + 
  geom_state_label()

prep reference data

usmapdata::us_map("states") %>% 
  select(state_name = full, state_abbr = abbr, geometry = geom) %>% 
  StatSf$compute_panel(coord = CoordSf) %>% 
  StatSfCoordinates$compute_group(coord = CoordSf) ->
usmaprefdata


usmapcrsinfo <- sf::st_crs(usmapdata::us_map("states"))

compute (join flat w/ reference)

compute_panel_us_states <- function(data, scales){
  
  inner_join(data, usmaprefdata)
  
}

ggplot2 extension magic - define stat

StatStates <- ggproto("StatStates",
                      Stat,
                      required_aes = "state_name|state_abbr",
                      compute_panel = compute_panel_us_states)

Use stat

state.name %>% 
  data.frame(state = .) %>% 
  mutate(is_aeiou = state %>% 
           str_detect("^[AEIOU]")) %>% 
  ggplot() + 
  aes(state_name = state) + 
  geom_sf(stat = StatStates) + 
  coord_sf(crs = usmapcrsinfo)

## Joining with `by = join_by(state_name)`

geom_sf

## function (mapping = aes(), data = NULL, stat = "sf", position = "identity", 
##     na.rm = FALSE, show.legend = NA, inherit.aes = TRUE, ...) 
## {
##     c(layer_sf(geom = GeomSf, data = data, mapping = mapping, 
##         stat = stat, position = position, show.legend = show.legend, 
##         inherit.aes = inherit.aes, params = list2(na.rm = na.rm, 
##             ...)), coord_sf(default = TRUE))
## }
## <bytecode: 0x7f861a437b20>
## <environment: namespace:ggplot2>