使用data.table上的geoosphere distm函数计算距离 [英] Using the geosphere distm function on a data.table to calculate distances

问题描述

我创建了一个包含6列的data.table。我的data.table有一个列包含两个位置：位置1和位置2.我试图使用distm函数来计算每行上的位置之间的距离，创建第7列。 geosphere包中的distM包需要针对每个lat / long组合计算两个不同的向量。我的代码下面不工作，所以我想弄清楚如何提供向量到函数。

  LOC_1_ID LOC1_LAT_CORD LOC1_LONG_CORD LOC_2_ID LOC2_LAT_CORD LOC2_LONG_CORD 
 1 35.68440 -80.48090 70624 34.86752 -82.46632 
 6 35.49770 -80.62870 70624 34.86752 -82.46632 
 10 35.66042 -80.50053 70624 34.86752 -82.46632 
  
 
 
 
假设res包含data.table，以下代码不起作用。
  res [，DISTANCE：= distm（c（LOC1_LAT_CORD，LOC1_LONG_CORD），c（LOC2_LAT_CORD，LOC2_LONG_CORD），fun = distHaversine）* 0.000621371] 
  
如果我要拉出每个向量的函数工作正常。
  loc1 < -  res [LOC1_ID == 1，。（LOC1_LAT_CORD，LOC1_LONG_CORD）] 
 loc2 < -  res [LOC2_ID == 70624，。（LOC2_LAT_CORD，LOC2_LONG_CORD）] 
 distm（loc1，loc2 ，fun = distHaversine）
  
真的，我的问题是如何应用函数来选择数据中的列。该函数需要向量作为参数。
解决方案
  distm  fucntion生成一组点的距离矩阵。如果你只是比较每一行上的点，并添加一列，你确定这是你想要的功能吗？
 
 
 
听起来你想要< c $ c> distHaversine 或 distGeo  
  library（data.table）
 library（geosphere）
 
 dt<  -  read.table（text =LOC_1_ID LOC1_LAT_CORD LOC1_LONG_CORD LOC_2_ID LOC2_LAT_CORD LOC2_LONG_CORD 
 1 35.68440 -80.48090 70624 34.86752 -82.46632 
 6 35.49770 -80.62870 70624 34.86752 -82.46632 
 10 35.66042 -80.50053 70624 34.86752 -82.46632，header = T）
 
 setDT（dt）
 dt [ ，distance_hav：= distHaversine（matrix（c（LOC1_LONG_CORD，LOC1_LAT_CORD），ncol = 2），
 matrix（c（LOC2_LONG_CORD，LOC2_LAT_CORD），ncol = 2））] 
 
＃LOC_1_ID LOC1_LAT_CORD LOC1_LONG_CORD LOC_2_ID LOC2_LAT_CORD LOC2_LONG_CORD distance_hav 
＃1：1 35.68440 -80.48090 70624 34.86752 -82.46632 202046.3 
＃2：6 35.49770 -80.62870 70624 34.86752 -82.46632 181310.0 
＃3：10 35.66042 -80.50053 70624 34.86752 -82.46632 199282.1 
  
 
I've created a data.table in that has 6 columns.  My data.table has a columns compairing two locations: Location 1 and Location 2.  I'm trying to use the distm function to calculate the distance between the locations on each row, creating a 7th column.  The distm package in the geosphere package requires two different vectors for each lat/long combo to be calculated against. My code below does not work, so I'm trying to figure out how to provide vectors to the function.
LOC_1_ID LOC1_LAT_CORD LOC1_LONG_CORD LOC_2_ID LOC2_LAT_CORD LOC2_LONG_CORD
 1       35.68440        -80.48090        70624    34.86752   -82.46632
 6       35.49770        -80.62870        70624    34.86752   -82.46632
10       35.66042        -80.50053        70624    34.86752   -82.46632
Assuming res holds the data.table the below code does not work.
 res[,DISTANCE := distm(c(LOC1_LAT_CORD, LOC1_LONG_CORD),c(LOC2_LAT_CORD, LOC2_LONG_CORD), fun=distHaversine)*0.000621371]
If I were to pull out each vector the function works fine.
loc1 <- res[LOC1_ID == 1,.(LOC1_LAT_CORD, LOC1_LONG_CORD)]
loc2 <- res[LOC2_ID==70624,.(LOC2_LAT_CORD, LOC2_LONG_CORD)]
distm(loc1, loc2, fun=distHaversine)
Really, my question is how to apply functions to select columns within a data.table when that function requires vectors as parameters.
解决方案
The distm fucntion generates a Distance matrix of a set of points. Are you sure this is the function you want if you're just comparing the points on each row, and adding one column?

It sounds like you actually want either distHaversine or distGeo
library(data.table)
library(geosphere)

dt <- read.table(text = "LOC_1_ID LOC1_LAT_CORD LOC1_LONG_CORD LOC_2_ID LOC2_LAT_CORD LOC2_LONG_CORD
1       35.68440        -80.48090        70624    34.86752   -82.46632
6       35.49770        -80.62870        70624    34.86752   -82.46632
10       35.66042        -80.50053        70624    34.86752   -82.46632", header = T)

setDT(dt)
dt[, distance_hav := distHaversine(matrix(c(LOC1_LONG_CORD, LOC1_LAT_CORD), ncol = 2),
                                   matrix(c(LOC2_LONG_CORD, LOC2_LAT_CORD), ncol = 2))]

#     LOC_1_ID LOC1_LAT_CORD LOC1_LONG_CORD LOC_2_ID LOC2_LAT_CORD LOC2_LONG_CORD distance_hav
# 1:        1      35.68440      -80.48090    70624      34.86752      -82.46632     202046.3
# 2:        6      35.49770      -80.62870    70624      34.86752      -82.46632     181310.0
# 3:       10      35.66042      -80.50053    70624      34.86752      -82.46632     199282.1


                        
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