Question

很多问题涉及重复观察的主题，但到目前为止，它们都没有对我有效。

在this questions中，我学会了如何从矢量中选择所有重复项。

# vector
id <- c("a","b","b","c","c","c","d","d","d","d")

#To return ALL duplicated values by specifying fromLast argument:
id[duplicated(id) | duplicated(id, fromLast=TRUE)]
## [1] "b" "b" "c" "c" "c" "d" "d" "d" "d"

#Yet another way to return ALL duplicated values, using %in% operator:
id[id %in% unique(id[duplicated(id)])]
## [1] "b" "b" "c" "c" "c" "d" "d" "d" "d"

现在有一个像这样的数据框：

dat <- data.frame(x = c(1, 1, 2, 2, 3), 
                  y = c(5, 5, 6, 7, 8), 
                  z = c('a', 'b', 'c', 'd', 'e'))

我如何选择同时具有x和y重复值的所有观测值，而不考虑z？

Answer 1

你可以这样使用data.table：

library(data.table)
setDT(dat)
# selects all (x,y) pairs that occur more than once
dat[ , if (.N > 1L) .SD, by = .(x, y)]

Answer 2

使用dplyr

的另一个选项

library(dplyr)
dat %>% group_by(x,y) %>% filter(n()>1) 

# A tibble: 2 x 3
#     x     y      z
#   <dbl> <dbl> <fctr>
#1    1     5      a
#2    1     5      b

Answer 3

在基地R

dat[ave(paste(dat$x,dat$y),dat$y,FUN=function(x) length(x))>1,]
  x y z
1 1 5 a
2 1 5 b

在R中，如何创建具有所有重复观察的子集数据框？

3 个答案: