在R中按组和ID计数观察值

Question

我正在试着写一个基于条件计算观察值的代码。我不知道这是否可能。我想要实现的是在组中只计算一个观察值，而不是将它们加在一起。

这是数据帧：

df <- structure(list(ID = c("P40", "P40", "P40", "P40", "P42", "P42",
                     "P43", "P43", "P43"), Year = c("2013", "2013", "2014", "2015", "2013", "2014", "2014", "2014", "2014"),
              Meeting = c("Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes")),
         class = "data.frame", row.names = c(NA, -9L))



ID  Year Meeting
P40 2013     Yes
P40 2013     Yes
P40 2014     Yes
P40 2015     Yes
P42 2013     Yes
P42 2014     Yes
P43 2014     Yes
P43 2014     Yes
P43 2014     Yes

我想要实现的结果是：

ID Year      Count
P40 2013     1
P40 2014     1
P40 2015     1
P42 2013     1
P42 2014     1
P43 2014     1

这就是我到目前为止的代码，它只计算所有的观察值。

df %>% group_by(ID, Year) %>% summarise(Count = n())

Answer 1

你想要的是：

count(df %>% distinct(ID, Year), ID, Year, name = 'Count')

输出：

# A tibble: 6 x 3
  ID    Year  Count
  <chr> <chr> <int>
1 P40   2013      1
2 P40   2014      1
3 P40   2015      1
4 P42   2013      1
5 P42   2014      1
6 P43   2014      1

Answer 2

我们可以在数据集上执行distinct，然后使用count

library(dplyr)
df %>% 
   distinct %>% 
   count(ID, Year)
# A tibble: 6 x 3
#  ID    Year      n
#  <chr> <chr> <int>
#1 P40   2013      1
#2 P40   2014      1
#3 P40   2015      1
#4 P42   2013      1
#5 P42   2014      1
#6 P43   2014      1

或者使用data.table

library(data.table)
unique(setDT(df[1:2]))[, .N, .(ID, Year)]

或者使用base R

subset(as.data.frame(table(unique(df[1:2]))), Freq != 0)

或cbind的一个选项

cbind(unique(df[1:2]), n = 1)

Answer 3

既然你只想在每组中有一个观察结果，这不是

transform(unique(df), count = 1)

#   ID Year Meeting count
#1 P40 2013     Yes     1
#3 P40 2014     Yes     1
#4 P40 2015     Yes     1
#5 P42 2013     Yes     1
#6 P42 2014     Yes     1
#7 P43 2014     Yes     1

或者，如果只想对选定的列进行检查

transform(unique(df[1:2]), count = 1)