Question

我有一个国家之间双边关系的数据框：

C1 C2
US FR
FR US
US DE
DE US
US RU
US FI
RU FI
FI RU

链接是定向链接，其中一些链接丢失（例如，我有US> RU，但没有RU> US）。我想找出所有唯一的配对。拥有这样的东西：

C1 C2 PairID
US FR 1
FR US 1
US DE 2
DE US 2
US RU -
US FI -
RU FI 3
FI RU 3

有什么建议吗？

Answer 1

这里是一种选择，假设您还希望计算像US>RU这样的非双向关系：

library(dplyr)
df %>%
        mutate(relation = paste(pmin(C1, C2), pmax(C1, C2), sep = "-"), #define the relation no matter the direction
               PairID = cumsum(c(1, head(relation, -1) != tail(relation, -1)))) %>% 
        select(-relation)
# output
  C1 C2 PairID
1 US FR      1
2 FR US      1
3 US DE      2
4 DE US      2
5 US RU      3
6 US FI      4
7 RU FI      5
8 FI RU      5

# Data: df
structure(list(C1 = c("US", "FR", "US", "DE", "US", "US", "RU", 
"FI"), C2 = c("FR", "US", "DE", "US", "RU", "FI", "FI", "RU")), .Names = c("C1", 
"C2"), class = "data.frame", row.names = c(NA, -8L))

Answer 2

我们可以创建一个字符串标识符，以捕获给定的一对国家/地区，而与它们的顺序无关：

library( tidyverse )

# Original data
X <- data_frame(C1 = c("US", "FR", "US", "DE", "US", "US", "RU", "FI"), 
            C2 = c("FR", "US", "DE", "US", "RU", "FI", "FI", "RU"))

# Creates an order-independent string ID for each entry
Y <- X %>% mutate( S = map2_chr( C1, C2, ~str_flatten(sort(c(.x,.y))) ) )
# # A tibble: 8 x 3
#   C1    C2    S    
#   <chr> <chr> <chr>
# 1 US    FR    FRUS 
# 2 FR    US    FRUS 
# 3 US    DE    DEUS 
# 4 DE    US    DEUS 
# 5 US    RU    RUUS 
# ...

然后，我们可以使用这些字符串标识符查找在两个方向上都出现的国家/地区对（例如US > FR和FR > US）。这些对将具有两个匹配的字符串ID。

# Identify string IDs with both orderings and assign an integer ID to each
Z <- Y %>% group_by(S) %>% filter( n() == 2 ) %>% ungroup %>%   # Keep groups of size 2
  select(S) %>% distinct %>% mutate( PairID = 1:n() )           # Annotate unique values
# # A tibble: 3 x 2
#   S     PairID
#   <chr>  <int>
# 1 FRUS       1
# 2 DEUS       2
# 3 FIRU       3

剩下要做的就是将新的字符串ID->整数ID映射与原始数据连接起来，并将NA替换为"-"：

left_join( Y, Z ) %>% select(-S) %>% mutate_at( "PairID", replace_na, "-")
# # A tibble: 8 x 3
#   C1    C2    PairID
#   <chr> <chr> <chr> 
# 1 US    FR    1     
# 2 FR    US    1     
# 3 US    DE    2     
# 4 DE    US    2     
# 5 US    RU    -     
# 6 US    FI    -     
# 7 RU    FI    3     
# 8 FI    RU    3

识别R中两列中的对

2 个答案: