Match function comes out as NA-CodePudding

I want to check where the characters in sentence is placed in alphabet_S.

I used match function but outcome is NA. Why is this happening?

sentence<-c("soccer is difficult")
sentence<-tolower(sentence)
sentence2<-strsplit(sentence, "")


alphabet_S<-c("a","b","c","d","e","f","g","h","i","j",
              "k","l","m","n","o","p","q","r","s","t",
              "u","v","w","x","y","z","next")


match(sentence2,alphabet_S)

CodePudding user response：

We need to extract the list element with [[ (or unlist if there are more than one elements in the list). The strsplit splits and returns a list

match(sentence2[[1]], alphabet_S)

-output

[1] 19 15  3  3  5 18 NA  9 19 NA  4  9  6  6  9  3 21 12 20

Checking the structure gives

> str(sentence2)
List of 1
 $ : chr [1:19] "s" "o" "c" "c" ...

CodePudding user response：

If you also want to cycle through larger lists with n entries you can use sapply

sapply(sentence2, match, alphabet_S)
      [,1]
 [1,]   19
 [2,]   15
 [3,]    3
 [4,]    3
 [5,]    5
 [6,]   18
 [7,]   NA
 [8,]    9
 [9,]   19
[10,]   NA
[11,]    4
[12,]    9
[13,]    6
[14,]    6
[15,]    9
[16,]    3
[17,]   21
[18,]   12
[19,]   20