我绘制的段的坐标

Question

我想删除区域外的小段（数据 = station_EVHOE）。 the map here

为此，我画了一条黑色线段来划分相关区域（即右侧区域）。 所以我想删除左侧区域中的点。

我的代码是用 ggplot 制作的：

 d <- ggplot() + 
  coord_map(xlim = c(-12,-1), ylim = c(43,52)) +
  geom_polygon(aes(x=longitude, y=latitude), data = coast_EVHOE) + 
  geom_segment(aes(x = longitude_début, y = latitude_début, xend = longitude_fin, yend = latitude_fin, colour = as.factor(annee)), data = station_EVHOE) + 
  geom_segment(aes(x = -4.374794, y = 47.7975, xend = -7.8694, yend = 43.773630))

那么，是否可以提取黑色部分的坐标，以去除右侧区域之外的点？

Answer 1

这里有一个基于此的想法：https://math.stackexchange.com/questions/274712/calculate-on-which-side-of-a-straight-line-is-a-given-point-located

#determine which station are on the right side of the line
#I use only one point, you can adapt to check if the two point of the station are on the right side of the plot

station_EVHOE$right_side = 
  ((station_EVHOE$longitude_début + 4.374794)*(43.773630 - 47.7975)) - 
  ((station_EVHOE$latitude_début - 47.7975)*(-7.8694 + 4.374794)) < 0

d <- ggplot() + 
  coord_map(xlim = c(-12,-1), ylim = c(43,52)) +
  geom_polygon(aes(x=longitude, y=latitude), data = coast_EVHOE) + 

# plot only the station at the right side of the line
  geom_segment(aes(x = longitude_début, y = latitude_début, xend = longitude_fin, yend = latitude_fin, colour = as.factor(annee)), data = station_EVHOE[station_EVHOE$right_side,]) + 
  geom_segment(aes(x = -4.374794, y = 47.7975, xend = -7.8694, yend = 43.773630))