[R] Error creating a map with packages sf and tidyverse.

[Bob Green]

I was hoping for advice about this code that I have run several 
times. When I recently ran the code, I received the error 
below:"Error in FUN(X[[i]], ...) : object 'fac' not found"

In R Studio the code runs, but instead of non-red countries being 
white, they are darker grey.

Is 'fill=fac', no longer valid, or is there some other issue?

Any advice is appreciated,

Regards

Bob

 > library(tidyverse)
-- Attaching packages 
----------------------------------------------------------------------------- 
tidyverse 1.3.1 --
v ggplot2 3.3.5     v purrr   0.3.4
v tibble  3.1.3     v dplyr   1.0.7
v tidyr   1.1.4     v stringr 1.4.0
v readr   2.1.1     v forcats 0.5.1
-- Conflicts 
-------------------------------------------------------------------------------- 
tidyverse_conflicts() --
x dplyr::filter() masks stats::filter()
x dplyr::lag()    masks stats::lag()
Warning messages:
1: In (function (kind = NULL, normal.kind = NULL, sample.kind = NULL)  :
   non-uniform 'Rounding' sampler used
2: In (function (kind = NULL, normal.kind = NULL, sample.kind = NULL)  :
   non-uniform 'Rounding' sampler used
 > library(sf)
Linking to GEOS 3.9.1, GDAL 3.2.1, PROJ 7.2.1; sf_use_s2() is TRUE
Warning message:
package 'sf' was built under R version 4.1.3
 >
 >
 >
 > world_sf = map_data("world") %>%
+    filter(region != "Antarctica") %>%
+    mutate(region=replace(region, subregion=="Alaska", "USA_Alaska")) %>%
+    st_as_sf(coords=c("long","lat"), crs=4326) %>%
+    group_by(region, group) %>% summarise(geometry=st_combine(geometry)) %>%
+    st_cast("POLYGON") %>% summarise(geometry=st_combine(geometry))
`summarise()` has grouped output by 'region'. You can override using 
the `.groups` argument.
 >
 > labs = tibble(region = c("Argentina", "Australia", 
"Barbados","Brazil", "England","Fiji", "France", "French Polynesia", 
"Ghana", "Italy","Japan", "New Zealand", "Papua New Guinea", "Peru", 
"Portugal", "Samoa", "Sao Tome and Principe", "Senegal", "Solomon 
Islands", "South Africa", "Spain", "Trinidad", "Tobago", "Turkey", 
"UK", "Uruguay", "USA"))
 > ggplot()+geom_sf(aes(fill=fac))+coord_sf(expand=FALSE)
Error in FUN(X[[i]], ...) : object 'fac' not found
 >
 > labels_sf =  st_point_on_surface(world_sf) %>% right_join(labs, by="region")
Warning messages:
1: In st_point_on_surface.sf(world_sf) :
   st_point_on_surface assumes attributes are constant over geometries of x
2: In st_point_on_surface.sfc(st_geometry(x)) :
   st_point_on_surface may not give correct results for longitude/latitude data
 >
 >
 > world_sf %>% mutate(fac = region %in% labs$region)  %>%
+    ggplot()+geom_sf(aes(fill=fac))+coord_sf( expand=FALSE)+
+    theme(axis.title = element_blank(), legend.position = "none")+
+    scale_fill_manual(values=c("FALSE"=NA, "TRUE"="red"))
 >