找出我的数据框中有多少点与区域shapefile重叠

Question

I have a dataframe containing list of all accidents and their locations (about 10,000 location coordinates) that took place in a city in a month.

Accident ID   Name         latitudes longitudes    Intensity  time
 1           citycentre     -25.5567   +54.00087     minor    morning
 2           
 3
 4

I need to find how many of those accidents took place between a given set of longitudes and latitudes.(eg between latitudes 25'S and 27'S, lontitudes 54 E and 55 E)

Is there a way to do such a thing on RI am new to R so any help will be much appreciated.I have to do the same process with data from a large number of months and between different pairs of coordinates.So running a loop and using a counter variable will be very time consuming.

Is there a functional available that will tell me the number of accidents if I make my study area into a polygon shape file

Answer 1

I'm sure there are many ways to do it. Here's just one using non-equi joins:

library(data.table)
points <- fread("Accident_ID   Name         latitudes longitudes    Intensity  time
 1           citycentre     -28.5567   +54.50087     minor    morning
 2           citycentre     -28.5567   +54.50087     minor    morning
 3           citycentre     0   0     minor    morning
 4           citycentre     100   100     minor    morning")
extents <- data.table(
  extent_id=1:3, 
  x1=c(-30, -20, 1000), 
  x2=c(-27, 20, 1100), 
  y1=c(54, -54, 100), 
  y2=c(55, 55, 100)
)
points[extents, on=.(latitudes>=x1, latitudes<=x2, longitudes>=y1, longitudes<=y2)][
  ,.(N=sum(!is.na(Accident_ID))), by=extent_id]
#    extent_id N
# 1:         1 2
# 2:         2 1
# 3:         3 0