unique() for more than one variable

Question

I have the following data frame in R:

> str(df)
\'data.frame\':   545227 obs. of  15 variables:
 $ ykod : int  93 93 93 93 93 93 93 93 93 93 ...
 $ yad  :         


        

Answer 1

This dplyr method works nicely when piping.

For selected columns:

library(dplyr)
iris %>% 
  select(Sepal.Width, Species) %>% 
  t %>% c %>% unique

 [1] "3.5"        "setosa"     "3.0"        "3.2"        "3.1"       
 [6] "3.6"        "3.9"        "3.4"        "2.9"        "3.7"       
[11] "4.0"        "4.4"        "3.8"        "3.3"        "4.1"       
[16] "4.2"        "2.3"        "versicolor" "2.8"        "2.4"       
[21] "2.7"        "2.0"        "2.2"        "2.5"        "2.6"       
[26] "virginica" 

Or for the whole dataframe:

iris %>% t %>% c %>% unique 

 [1] "5.1"        "3.5"        "1.4"        "0.2"        "setosa"     "4.9"       
 [7] "3.0"        "4.7"        "3.2"        "1.3"        "4.6"        "3.1"       
[13] "1.5"        "5.0"        "3.6"        "5.4"        "3.9"        "1.7"       
[19] "0.4"        "3.4"        "0.3"        "4.4"        "2.9"        "0.1"       
[25] "3.7"        "4.8"        "1.6"        "4.3"        "1.1"        "5.8"       
[31] "4.0"        "1.2"        "5.7"        "3.8"        "1.0"        "3.3"       
[37] "0.5"        "1.9"        "5.2"        "4.1"        "5.5"        "4.2"       
[43] "4.5"        "2.3"        "0.6"        "5.3"        "7.0"        "versicolor"
[49] "6.4"        "6.9"        "6.5"        "2.8"        "6.3"        "2.4"       
[55] "6.6"        "2.7"        "2.0"        "5.9"        "6.0"        "2.2"       
[61] "6.1"        "5.6"        "6.7"        "6.2"        "2.5"        "1.8"       
[67] "6.8"        "2.6"        "virginica"  "7.1"        "2.1"        "7.6"       
[73] "7.3"        "7.2"        "7.7"        "7.4"        "7.9" 

Answer 2

How about using unique() itself?

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

Answer 3

There are a few ways to get all unique combinations of a set of factors.

with(df, interaction(yad, per, drop=TRUE))   # gives labels
with(df, yad:per)                            # ditto

aggregate(numeric(nrow(df)), df[c("yad", "per")], length)    # gives a data frame

Answer 4

This is an addition to Josh's answer.

You can also keep the values of other variables while filtering out duplicated rows in data.table

Example:

library(data.table)

#create data table
dt <- data.table(
  V1=LETTERS[c(1,1,1,1,2,3,3,5,7,1)],
  V2=LETTERS[c(2,3,4,2,1,4,4,6,7,2)],
  V3=c(1),
  V4=c(2) )

> dt
# V1 V2 V3 V4
# A  B  1  2
# A  C  1  2
# A  D  1  2
# A  B  1  2
# B  A  1  2
# C  D  1  2
# C  D  1  2
# E  F  1  2
# G  G  1  2
# A  B  1  2

# set the key to all columns
setkey(dt)

# Get Unique lines in the data table
unique( dt[list(V1, V2), nomatch = 0] ) 

# V1 V2 V3 V4
# A  B  1  2
# A  C  1  2
# A  D  1  2
# B  A  1  2
# C  D  1  2
# E  F  1  2
# G  G  1  2

Alert: If there are different combinations of values in the other variables, then your result will be

unique combination of V1 and V2