Issue in creating polygon in ggplot in R

Question

Why does my polygon look like two triangles instead of a box? Can some help explain how I can turn the polygon into a box?

data <- structure(list(AREA = c("a", "a", "b", "b"), Lat = c(43.68389835, 
43.68389835, 44.3395883, 44.3395883), Long = c(-88.22909367, 
-88.99888743, -88.22909367, -88.99888743)), row.names = c(NA, 
-4L), spec = structure(list(cols = list(AREA = structure(list(), class = c("collector_character", 
"collector")), Lat = structure(list(), class = c("collector_double", 
"collector")), Long = structure(list(), class = c("collector_double", 
"collector"))), default = structure(list(), class = c("collector_guess", 
"collector")), delim = ","), class = "col_spec"), problems = <pointer: 0x000002548f014500>, class = c("spec_tbl_df", 
"tbl_df", "tbl", "data.frame"))

Code

library(tidyverse)
ggplot() + geom_polygon(data=data, mapping=aes(x=Long, y=Lat))

Answer 1

Currently geom_polygon draws the polygon in exactly the order of the points as given in data . To have a closed polygon, you need to order your points appropriately, either clockwise or anti-clockwise.

We can do this by calculating the angle relative to the lat/long centre , and then order points according to that angle.

library(tidyverse)
data %>%
    mutate(angle = atan2(Lat - mean(Lat), Long - mean(Long))) %>%
    arrange(desc(angle)) %>%
    ggplot() + 
    geom_polygon(aes(x = Long, y = Lat))