Get all possible string sequences where each element comes from different set in R

问题

Assume I have 4 vectors of character elements:

s1 <- c("o", "ó")
s2 <- c("c", "ć")
s3 <- c("o", "ó")
s4 <- c("z", "ź", "ż")

I want to build 4-element vectors that are all possible combinations of elements from s1, s2, s3, s4 in a way that in one of a result vectors 1-st, -2nd, 3-rd and 4-th element comes from s1, s2, s3, s4, respectively.

For example, I would like to get the following result vectors:

[1] "o", "c", "o", "z"
[1] "ó", "c", "o", "z"
[1] "o", "ć", "o", "z"

...

[My general goal of it is to produce all possible words from a given word in my native, assuming the given word have some diacritic marks ommited. I firstly extract all character candidates for being a diacritic mark and then want to inject them or their diacritic equivalents.]

回答1:

It's not super elegant but using the definitions for s1-s4 above, here is a quick for loop of for loops that will print the vectors you requested.

for(a in s1){
  for(b in s2){
    for(c in s3){
      for(d in s4){
        print(c(a,b,c,d))
      }
    }
  }
}

Output:

[1] "o" "c" "o" "z"
[1] "o" "c" "o" "z"
[1] "o" "c" "o" "z"
[1] "o" "c" "ó" "z"
[1] "o" "c" "ó" "z"
[1] "o" "c" "ó" "z"
[1] "o" "c" "o" "z" 
[...]

As shadow said above, expand.grid() is a much more elegant solution:

expand.grid(list(s1,s2,s3,s4))

Output:

   Var1 Var2 Var3 Var4
1     o    c    o    z
2     ó    c    o    z
3     o    c    o    z
4     ó    c    o    z
5     o    c    ó    z
6     ó    c    ó    z
7     o    c    ó    z
8     ó    c    ó    z
[...]

回答2:

You may also check data.table

library(data.table)
res <- CJ(s1=s1,s2=s2,s3=s3,s4=s4) #order the result by columns

Checking with results obtained from expand.grid

res2 <- expand.grid(s1=s1,s2=s2,s3=s3,s4=s4,stringsAsFactors=F)
res2New <- res2[with(res2, order(s1,s2,s3,s4)),]
all.equal(res2New, as.data.frame(res),check.attributes=F)
#[1] TRUE

来源：https://stackoverflow.com/questions/24506602/get-all-possible-string-sequences-where-each-element-comes-from-different-set-in

标签

string

combinations

permutation

diacritics