Question

我正在尝试建立一个脚本，以查找轨迹上的点是否在多边形的一定距离内。就上下文而言，我使用两个数据集：第一个是HYSPLIT模型的结果，该模型显示了空气轨迹以及该空气包裹在特定时间的预期位置。第二个是县内邮政编码中心的数据框。

我的目标是邮政编码的质心，如果是，它是哪个邮政编码，在什么时间发生？


traj <- data.frame(
    hour = c(0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23),
    lat = c(33.176, 33.236, 33.304, 33.397, 33.536, 33.693, 33.850, 34.011,
            34.181, 34.382, 34.612, 34.825, 35.025, 35.210, 35.382, 35.511, 
            35.558, 35.640, 35.715, 35.795, 35.845, 35.885, 35.918, 35.927),
    lon = c(-115.623, -115.488, -115.322, -115.132, -114.938, -114.787, -114.699, 
            -114.640, -114.561, -114.472, -114.399,-114.324, -114.207, -114.050, 
            -113.794, -113.280, -112.605, -111.907, -111.230, -110.708, -110.036, 
            -109.314, -108.520, -107.810),
    date = c(2012-03-01 00:00:00, 2012-03-01 01:00:00, 2012-03-01 02:00:00, 2012-03-01 03:00:00, 
             2012-03-01 04:00:00, 2012-03-01 05:00:00, 2012-03-01 06:00:00, 2012-03-01 07:00:00, 
             2012-03-01 08:00:00, 2012-03-01 09:00:00, 2012-03-01 10:00:00, 2012-03-01 11:00:00, 
             2012-03-01 12:00:00, 2012-03-01 13:00:00, 2012-03-01 14:00:00, 2012-03-01 15:00:00, 
             2012-03-01 16:00:00, 2012-03-01 17:00:00, 2012-03-01 18:00:00, 2012-03-01 19:00:00,
             2012-03-01 20:00:00, 2012-03-01 21:00:00)
)

#Convert hysplit data frame to an sf object
traj.sf <- st_as_sf(traj, coords = c("lon", "lat"), crs=4326)
traj.sf
plot(traj.sf$geometry)


#Create the same dataframe for median pop centroids

medpop <- data.frame(
  longitude = c(-116.305303, -115.524899, -115.497389, -115.514936, 
                -115.566751, -115.505786, -115.361211, -115.575202, 
                -115.535597, -115.993063, -114.73435, -115.692165, 
                -116.040401, -115.956263, -115.621221, -114.628562), 
  latitude = c(33.211896, 32.980541, 32.680197, 33.127061, 
               32.784691, 32.729742, 32.807613, 32.848569, 
               33.280736, 32.734248, 33.372017, 32.795324, 
               33.409293, 33.289944, 33.039245, 32.77435), 

  Name = c("92004", "92227", "92231", "92233", "92243", "92249", "92250", "92251", 
           "92257", "92259", "92266", "92273", "92274", "92275", "92281", "92283"))
medpop

#convert the population centroid points data frame to an sf object
centroids <- st_as_sf(medpop, coords = c("longitude", "latitude"), crs=4326)
centroids

#Buffer the points
buffers <- st_buffer(centroids, dist = 0.2)

#Finding points within centroid buffers
over <- st_intersects(buffers, traj.sf)

我尝试使用sf包中的st_intersects。我遇到的问题是R似乎正在返回对象列表，但是我实际上需要知道相交何时发生以及该点实际上在哪个邮政编码附近。

我是GIS的R的新手，所以非常感谢！

Answer 1

使用功能st_intersection而不是st_intersects解决了此问题。这将返回数据框而不是列表：

over <- st_intersection(bufers, traj.sf) 
### the polygon, followed by the points that might cross the polygon

````

Answer 2

您在正确的轨道上，然后关闭...

您将需要利用sparse = F的{{1}}设置来获取向量，然后使用它来对sf::st_intersects数据帧进行子集化。

我正在绘制结果，我希望红点（已与轨迹相交的缓冲区的质心）是您想要的...

centroids

使用R查找哪些点位于缓冲区内？

2 个答案: