Removing duplicates for each ID

问题

Suppose that there are three variables in my data frame (mydata): 1) id, 2) case, and 3) value.

mydata <- data.frame(id=c(1,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4), case=c("a","b","c","c","b","a","b","c","c","a","b","c","c","a","b","c","a"), value=c(1,34,56,23,34,546,34,67,23,65,23,65,23,87,34,321,87))


mydata 
    id case value
1   1    a     1
2   1    b    34
3   1    c    56
4   1    c    23
5   1    b    34
6   2    a   546
7   2    b    34
8   2    c    67
9   2    c    23
10  3    a    65
11  3    b    23
12  3    c    65
13  3    c    23
14  4    a    87
15  4    b    34
16  4    c   321
17  4    a    87

For each id, we could have similar ‘case’ characters, and their values could be the same or different. So basically, if their values are the same, I only need to keep one and remove the duplicate.

My final data then would be

    id case value
1   1    a     1
2   1    b    34
3   1    c    56
4   1    c    23
5   2    a   546
6   2    b    34
7   2    c    67
8   2    c    23
9   3    a    65
10  3    b    23
11  3    c    65
12  3    c    23
13  4    a    87
14  4    b    34
15  4    c   321

回答1:

You could try duplicated

 mydata[!duplicated(mydata[,c('id', 'case', 'value')]),]
 #     id case value
 #1   1    a     1
 #2   1    b    34
 #3   1    c    56
 #4   1    c    23
 #6   2    a   546
 #7   2    b    34
 #8   2    c    67
 #9   2    c    23
 #10  3    a    65
 #11  3    b    23
 #12  3    c    65
 #13  3    c    23
 #14  4    a    87
 #15  4    b    34
 #16  4    c   321

Or use unique with by option from data.table

 library(data.table)
 set.seed(25)
 mydata1 <- cbind(mydata, value1=rnorm(17))
 DT <- as.data.table(mydata1)
 unique(DT, by=c('id', 'case', 'value'))
 #   id case value      value1
 #1:  1    a     1 -0.21183360
 #2:  1    b    34 -1.04159113
 #3:  1    c    56 -1.15330756
 #4:  1    c    23  0.32153150
 #5:  2    a   546 -0.44553326
 #6:  2    b    34  1.73404543
 #7:  2    c    67  0.51129562
 #8:  2    c    23  0.09964504
 #9:  3    a    65 -0.05789111
 #10: 3    b    23 -1.74278763
 #11: 3    c    65 -1.32495298
 #12: 3    c    23 -0.54793388
 #13: 4    a    87 -1.45638428
 #14: 4    b    34  0.08268682
 #15: 4    c   321  0.92757895

回答2:

To add to the other answers, here's a dplyr approach:

library(dplyr)
mydata %>% group_by(id, case, value) %>% distinct()

mydata %>% distinct(id, case, value)

回答3:

Case and value only? Easy:

> mydata[!duplicated(mydata[,c("id","case","value")]),]

Even if you have a ton more variables in the dataset, they won't be considered by the duplicated() call.

来源：https://stackoverflow.com/questions/27255065/removing-duplicates-for-each-id

标签

dataframe

duplicates