Question

I have the data.frame

df<-data.frame("Site.1" = c("A", "B", "C"),
               "Site.2" = c("D", "B", "B"),
               "Tsim" = c(2, 4, 7), 
               "Jaccard" = c(5, 7, 1))

#    Site.1 Site.2 Tsim Jaccard
#  1      A      D    2       5
#  2      B      B    4       7
#  3      C      B    7       1

I can get the unique levels for each column using

top.x<-unique(df[1:2,c("Site.1")])
top.x

# [1] A B
# Levels: A B C

top.y<-unique(df[1:2,c("Site.2")])
top.y

# [1] D B
# Levels: B D

How do I get the unique levels for both columns and turn them into a vector i.e:

v <- c("A", "B", "D")
v
# [1] "A" "B" "D"

Answer 1

top.xy <- unique(unlist(df[1:2,]))
top.xy

[1] A B D
Levels: A B C D