Unique combination of all elements from two (or more) vectors

Question

I am trying to create a unique combination of all elements from two vectors of different size in R.

For example, the first vector is

a <- c(\"ABC\         


        

Answer 1

Missing in this r-faq overview is the CJ-function from the data.table-package. Using:

library(data.table)
CJ(a, b, unique = TRUE)

gives:

      a          b
 1: ABC 2012-05-01
 2: ABC 2012-05-02
 3: ABC 2012-05-03
 4: ABC 2012-05-04
 5: ABC 2012-05-05
 6: DEF 2012-05-01
 7: DEF 2012-05-02
 8: DEF 2012-05-03
 9: DEF 2012-05-04
10: DEF 2012-05-05
11: GHI 2012-05-01
12: GHI 2012-05-02
13: GHI 2012-05-03
14: GHI 2012-05-04
15: GHI 2012-05-05

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_{NOTE: since version 1.12.2 CJ autonames the resulting columns (see also here and here).}