r - 在 r 中的形状内创建随机点

Question

我正在尝试为一个项目模拟一些数据，基本上我需要绘制一个不规则的椭圆形形状，然后在该形状内制作一堆随机点，我完全不知道如何做到这一点。
现在，我已经制作了一个样条形状，然后在它上面绘制了一堆点。有没有办法找到重叠？或者更好，只是在预制形状的边界内生成随机点？
(如果有更好的开始方式，请随意放弃我的代码 - 也许它需要某种空间对象？)

set.seed(2)
shape <- data.frame(
  x     = c(2, 3, 2, 3, 2, 1, 0, 1),
  y     = c(1, 3, 5, 7, 9, 7, 5, 3 )
)

scatter = data.frame(
  x = rnorm(100, mean = 1.5, sd = .6),
  y = rnorm(100, mean = 5, sd = 2)
)


ggplot(data = shape, 
       aes(x=x,y=y)) +
  ggforce::geom_bspline_closed(fill = "transparent", color = "black") +
  geom_point(color = "blue") +
  coord_equal() +  
  geom_point(data = scatter, shape = "*", size=3)

Answer 1

我会推荐 sf包，因为它是为空间数据和执行空间操作而制作的。这是在多边形内生成随机点的一个小例子:

library(ggplot2)

polygon =
  # The syntax for creating a polygon with sf is a little strange.
  # It has to be a list of matrices and the first point has to be 
  # repeated as the last point (2, 1).
  list(
    matrix(
      c(2, 1, 3, 3, 2, 5, 3, 7, 2, 9, 1, 7, 0, 5, 1, 3, 2, 1),
      ncol=2, byrow=T
    )
  ) 

# Create an sf polygon
polygon = sf::st_polygon(polygon)
# Sample 50 random points within the polygon
points = sf::st_sample(polygon, size=50)

# Plot using the ggplot geom_sf function.
ggplot() + 
  geom_sf(aes(), data=polygon) + 
  geom_sf(aes(), data=points)

如果您需要点的坐标，您可以简单地将 sf 点对象转换为 data.frame与 points %>% sf::st_coordinates() %>% as.data.frame() .