如何从 R 中的 data.frame 中提取唯一元素？

Question

Can someone suggest a way to extract unique elements from a data.frame?

I have noticed unique , but since it works on either rows or columns, it doesn't do what I'm looking for. I'm after unique cells from a data.frame.

eg,

df<-data.frame(V1=c("Hello","fat","man"),V2=c("cat","fat","Hello"),V3=c("man","dog","black"))

Extracting unique elements should give me c("Hello","fat","man","cat","dog","black")

Answer 1

A 'data.frame' can be considered as a 'list' with columns as 'list' elements having the same length. By using unlist , we can convert it to vector and then get the unique values and convert to 'character' class with as.character .

as.character(unique(unlist(df)))

Answer 2

Or simply:

unique(as.vector(as.matrix(df)))
## [1] "Hello" "fat"   "man"   "cat"   "dog"   "black"