我绘制的线段坐标

Question

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

为此，我画了一个黑色的线段，划定了相关的区域（这是右边的区域）。 所以我想删除左侧区域的点。

我的代码与ggplot制作：

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，是不是可以提取黑色分割的坐标，为了改掉正确的区域外点？

Answer 1

这里基于这一点的想法：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))