r - unique() 用于多个变量

Question

我在 R 中有以下数据框:

> str(df)
'data.frame':   545227 obs. of  15 variables:
 $ ykod : int  93 93 93 93 93 93 93 93 93 93 ...
 $ yad  : Factor w/ 42 levels "BAKUGAN","BARBIE",..: 30 30 30 30 30 30 30 30 30 30 ...
 $ per  : Factor w/ 3 levels "2 AYLIK","3 AYLIK",..: 3 3 3 3 3 3 3 3 3 3 ...
 $ donem: int  201101 201101 201101 201101 201101 201101 201101 201101 201101 201101 ...
 $ sayi : int  201101 201101 201101 201101 201101 201101 201101 201101 201101 201101 ...
 $ mkod : int  4 5 9 11 12 18 20 22 25 26 ...
 $ mad  : Factor w/ 10464 levels "   Defne Market          ",..: 405 8075 9710 10145 9297 7973 2542 3892 2759 5769 ...
 $ mtip : Factor w/ 29 levels "Abone Bürosu                                      ",..: 2 20 20 2 2 2 2 2 2 2 ...
 $ kanal: Factor w/ 2 levels "OB","SS": 2 2 2 2 2 2 2 2 2 2 ...
 $ bkod : int  110565 110565 110565 110565 110565 110565 110565 110565 110565 110565 ...
 $ bad  : Factor w/ 212 levels "4. Levent","500 Evler",..: 167 167 167 167 167 167 167 167 167 167 ...
 $ bolge: Factor w/ 12 levels "Adana Şehiriçi",..: 7 7 7 7 7 7 7 7 7 7 ...
 $ sevk : int  2 3 3 3 2 2 2 6 2 2 ...
 $ iade : int  2 1 0 2 0 2 1 0 0 2 ...
 $ satis: int  0 2 3 1 2 0 1 6 2 0 ...

我想列出所选多个变量的唯一值(如 SQL 的 DISTINCT)。例如，unique(yad) 给出了每 42 个元素的名称，但我需要提取两列(yad 和 per 在一起，具有所有独特的组合):

yad           per
---           ---
BARBIE        AYLIK
BAKUGAN       2 AYLIK
MICKEY MOUSE  2 AYLIK
TINKERBELL    3 AYLIK
...           ...

我怎样才能实现这个目标？

Answer 1

使用 unique() 本身怎么样？

df <- data.frame(yad = c("BARBIE", "BARBIE", "BAKUGAN", "BAKUGAN"),
                 per = c("AYLIK",  "AYLIK",  "2 AYLIK", "2 AYLIK"),
                 hmm = 1:4)

df
#       yad     per hmm
# 1  BARBIE   AYLIK   1
# 2  BARBIE   AYLIK   2
# 3 BAKUGAN 2 AYLIK   3
# 4 BAKUGAN 2 AYLIK   4

unique(df[c("yad", "per")])
#       yad     per
# 1  BARBIE   AYLIK
# 3 BAKUGAN 2 AYLIK