R：根据变量查找非唯一的整体

Question

我在表达这一权利时遇到了问题，如果有任何编辑，我将不胜感激。我有一个看起来像这样的 data frame，显示各种卫星的运营商：

Operator Satellite
United   SAT1
American SAT2
United   SAT1
United   SAT3
American SAT3
American SAT5
Delta    SAT1
United   SAT8

我正在尝试获得一个 data frame 给我的条目，对于由多个运营商运营的卫星，列出两个变量：

Operator Satellite
United   SAT1
United   SAT1
Delta    SAT1
United   SAT3
American SAT3

我能够解决这个问题的唯一方法是使用 which(file$operator) 循环，但这似乎是一种不必要的麻烦方法。

我将不胜感激任何帮助，并且对任何 packages 没有偏好。提前谢谢你。

Answer 1

这是一个data.table单行方法

library( data.table )
DT <- fread("Operator Satellite
            United   SAT1
            American SAT2
            United   SAT1
            United   SAT3
            American SAT3
            American SAT5
            Delta    SAT1
            United   SAT8")


DT[, if( .N > 1 ) .SD, by = Satellite]

#    Satellite Operator
# 1:      SAT1   United
# 2:      SAT1   United
# 3:      SAT1    Delta
# 4:      SAT3   United
# 5:      SAT3 American

Answer 2

你可以试试dplyr解决办法：

library(dplyr)

df <- structure(list(Operator = c("United", "American", "United", "United", 
"American", "American", "Delta", "United"), Satellite = c("SAT1", 
"SAT2", "SAT1", "SAT3", "SAT3", "SAT5", "SAT1", "SAT8")), class = "data.frame", row.names = c(NA, 
-8L))

#Code
df %>% left_join(df %>% group_by(Satellite) %>% summarise(N=n())) %>% filter(N>1)

  Operator Satellite N
1   United      SAT1 3
2   United      SAT1 3
3   United      SAT3 2
4 American      SAT3 2
5    Delta      SAT1 3

Answer 3

这是一种没有额外包的单行方法

dw <- read.table(header=T, text='
Operator Satellite
United   SAT1
American SAT2
United   SAT1
United   SAT3
American SAT3
American SAT5
Delta    SAT1
United   SAT8 
 ')

  dw[ave(dw$Satellite, dw$Satellite,  FUN = length) > 1,]

  Operator Satellite
1   United      SAT1
3   United      SAT1
4   United      SAT3
5 American      SAT3
7    Delta      SAT1

R：根据变量查找非唯一的整体

R: Find non-unique entires based on a variable

r

unique

dataframe