Random Shape with sf - geometry

Random Shapes with sf.r

rm(list = ls())


library(sf)
library(tidyverse)
library(ggthemes)

## Generate some random data
df <- tibble(
  grp = sample(LETTERS[1:18], size=300, replace=T),
  x = rbeta(n=300, shape1=1, shape2=1),
  y = rbeta(n=300, shape1=1.5, shape2=2),
) %>% mutate(idx=as.numeric(factor(grp))-1,
             y = (idx%%3)+y,
             x = floor(idx/3)+x) 

## Rotate Function  
rot = function(a) matrix(c(cos(a), sin(a), -sin(a), cos(a)), 2, 2)
rot(pi/2)


df_sf <-df %>% 
  st_as_sf(coords=c("x","y"), dim="XY") %>%
  #st_set_crs(4326) %>%
  group_by(grp) %>%
  summarise(geometry = st_combine(geometry),
            center = st_centroid(geometry),
            geom_hull = st_convex_hull(geometry),
            geom_hull_rot = (geom_hull - center) * rot(pi/2) + center ) %>%
  st_cast("LINESTRING") %>%
  st_cast("POLYGON") 


df_sf

df_sf %>% ggplot() + 
  geom_sf(aes(fill=grp), color="#ffffff", size=0, alpha=0.5) + 
  geom_sf(aes(color=grp, geometry=geom_hull),fill="#ffffff00",size=1) +
  geom_sf(aes(color=grp, geometry=geom_hull_rot), fill="#ffffff00", size=1) +
  geom_sf(aes(geometry=center), shape=4, color="white") +
  scale_fill_tableau("Hue Circle", guide="none") +
  scale_color_tableau("Hue Circle", guide="none") +
  theme_void() +
  theme(plot.background = element_rect(fill="gray8")) +
  expand_limits(x=c(0,6), y=c(-0.5,3.5)) ## just giving extra space 

ggsave(file="~/Downloads/RandomShape.png", width=12, height=8)