我有一個事件位置(經度,緯度)的大型數據框。看到下面的示例:R地圖 - 在地圖上繪製點時過濾器座標輸出
events <- structure(list(lat = c(45.464944, 40.559207, 45.956775, 44.782831, 45.810287, 35.913357, 43.423855, 45.2359, 45.526025, 41.91371, 46.340833, 40.696482, 42.367164, 41.913701, 41.89167, 46.046206, 41.108316, 45.514132, 45.688118, 37.090387, 43.446555, 41.913712, 46.614833, 45.368825, 41.892168), lon = c(9.163453, 8.321587, 12.983347, 10.886471, 9.077844, 10.560439, 6.768272, 9.23176, 9.375761, 12.466994, 6.889444, 17.316925, 13.352248, 12.466992, 12.516713, 14.497758, 16.871019, 12.056176, 9.176543, 15.293506, 6.77119, 12.466993, 15.194904, 11.110711, 12.516085)), .Names = c("lat", "lon"), row.names = c(NA, 25L), class = "data.frame")
我想只繪製發生在特定國家(例如,意大利)的事件。
以下地塊的所有事件:
library(rworldmap)
library(maps)
par(mar=c(0,0,0,0))
plot(getMap(resolution="low"), xlim = c(14,14), ylim = c(36.8,47))
points(x=events$lon, y=events$lat, pch = 19, col ='red' , cex = 0.6)
我怎樣才能篩選出屬於國家的邊界以外的事件?預先感謝您的幫助和支持。
看看'SP :: over'。你可以用它來過濾只有特定多邊形中的點。 – hrbrmstr 2015-02-23 11:47:49