用于计算包含xy坐标列表的数据帧中的所有点之间的距离的方法

Question

我确定之前已经回答了这个问题,但我无法找到生命中的线索!

我试图使用r来生成数据帧中xy坐标对之间所有距离的列表.数据存储如下:

ID = c('1','2','3','4','5','6','7')
x = c(1,2,4,5,1,3,1)
y = c(3,5,6,3,1,5,1)
df= data.frame(ID,x,y)

目前我可以使用以下方法计算两点之间的距离:

length = sqrt((x1 - x2)^2+(y1 - y2)^2).

但是,我不确定下一步该去哪里.我应该使用plyr或for循环中的东西吗？

谢谢你的帮助!

Answer 1

你试过吗？dist,你列出的公式是欧几里德距离

dist(df[,-1]) 

Answer 2

You can use a self-join to get all combinations then apply your distance formula. All of this is easily do-able using the tidyverse (combination of packages from Hadley Wickham):

# Load the tidyverse
library(tidyverse)

# Set up a fake key to join on (just a constant)
df <- df %>% mutate(k = 1) 

# Perform the join, remove the key, then create the distance
df %>% 
 full_join(df, by = "k") %>% 
 mutate(dist = sqrt((x.x - x.y)^2 + (y.x - y.y)^2)) %>%
 select(-k)

N.B. using this method, you'll also calculate the distance between each point and itself (as well as with all other points). It's easy to filter those points out though:

df %>% 
 full_join(df, by = "k") %>% 
 filter(ID.x != ID.y) %>%
 mutate(dist = sqrt((x.x - x.y)^2 + (y.x - y.y)^2)) %>%
 select(-k)

For more information about using the tidyverse set of packages I'd recommend R for Data Science or the tidyverse website.