从 R 中的数据框中删除重复的列组合

Question

我想从以下数据中删除 sessionid、qf 和 qn 的重复组合

               sessionid             qf        qn         city
1  9cf571c8faa67cad2aa9ff41f3a26e38     cat   biddix          fresno
2  e30f853d4e54604fd62858badb68113a   caleb     amos                
3  2ad41134cc285bcc06892fd68a471cd7  daniel  folkers                
4  2ad41134cc285bcc06892fd68a471cd7  daniel  folkers                
5  63a5e839510a647c1ff3b8aed684c2a5 charles   pierce           flint
6  691df47f2df12f14f000f9a17d1cc40e       j    franz prescott+valley
7  691df47f2df12f14f000f9a17d1cc40e       j    franz prescott+valley
8  b3a1476aa37ae4b799495256324a8d3d  carrie mascorro            brea
9  bd9f1404b313415e7e7b8769376d2705    fred  morales       las+vegas
10 b50a610292803dc302f24ae507ea853a  aurora      lee                
11 fb74940e6feb0dc61a1b4d09fcbbcb37  andrew    price       yorkville 

我将数据作为 data.frame 读入并将其称为 mydata。这是我到目前为止的代码，但我需要知道如何首先对 data.frame 进行正确排序。其次去除sessionid、qf、qn的重复组合。最后在列 qf 中绘制直方图字符

sortDATA<-function(name)
{
#sort the code by session Id, first name, then last name
sort1.name <- name[order("sessionid","qf","qn") , ]
#create a vector of length of first names
sname<-nchar(sort1.name$qf)
hist(sname)
}

谢谢!

Answer 1

duplicated()有 data.frame 的方法s，它专为此类任务而设计:

df <- data.frame(a = c(1:4, 1:4), 
                 b = c(4:1, 4:1), 
                 d = LETTERS[1:8])

df[!duplicated(df[c("a", "b")]),]
#   a b d
# 1 1 4 A
# 2 2 3 B
# 3 3 2 C
# 4 4 1 D