问题
Using the variables alpha and key, encrypt ptext into a variable named ctext. Using substitution cipher
So I have a text file separated in a vector
ptext <- strsplit(ptext,split = "", fixed = TRUE) ptext <- unlist(ptext)
I also created a key for this cipher
key <- "ZGYHXIWJVKULTMSARBQCPDOENF"
key <- unlist(strsplit(key,""))
and an Alphabet vector for the key
alpha <- "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
alpha <= toupper(alpha)
alpha <- unlist(strsplit(alpha,""))
Now my goal is to try to replace all the character in the ptext vector corresponding to the letters in the key in relation to alpha (Example: A in alpha in relation to Z in the key. So all A's in the text would be replaced by a Z)
I know I am supposed to match the alpha in key
cipher <- match(key,alpha)
Now my issue is, the ptext file is over 1000 characters in it. How would I be able to replace all the letters in that vector?
回答1:
You could use chartr which will avoid splitting the string and pasting back.
ptext <- 'REQWDSFFFSLK'
alpha <- 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
key <- 'ZGYHXIWJVKULTMSARBQCPDOENF'
chartr(alpha, key, ptext)
#[1] "BXROHQIIIQLU"
Here, all R is replaced with B, E with X and so on for every character value.
回答2:
Basically, you need to do what you are doing with the cipher but apply that to each letter of ptext. You can either leave as a vector of single strings or put back together as desired, for example using paste0 below.
set.seed(123)
ptext <- strsplit(LETTERS[sample(26, 100, T)],split = "", fixed = TRUE)
ptext <- unlist(ptext)
key <- "ZGYHXIWJVKULTMSARBQCPDOENF"
key <- unlist(strsplit(key,""))
alpha <- unlist(strsplit(LETTERS,""))
encoded <- sapply(ptext, function(x) key[match(x, alpha)])
encoded
#> O S N C J R V K E T N V Y Z E S Y Y I C
#> "S" "Q" "M" "Y" "K" "B" "D" "U" "X" "C" "M" "D" "N" "F" "X" "Q" "N" "N" "V" "Y"
#> H Z G J I S D N Q K G U L O J M G I I J
#> "J" "F" "W" "K" "V" "Q" "H" "M" "R" "U" "W" "P" "L" "S" "K" "T" "W" "V" "V" "K"
#> W U G U F Y B E H L M R A Y Y F U O I O
#> "O" "P" "W" "P" "I" "N" "G" "X" "J" "L" "T" "B" "Z" "N" "N" "I" "P" "S" "V" "S"
#> Z P T F K H V V G P Q V R Q B D M E V S
#> "F" "A" "C" "I" "U" "J" "D" "D" "W" "A" "R" "D" "B" "R" "G" "H" "T" "X" "D" "Q"
#> Y T V Y N Y W C H P L Y N C N G C W V Z
#> "N" "C" "D" "N" "M" "N" "O" "Y" "J" "A" "L" "N" "M" "Y" "M" "W" "Y" "O" "D" "F"
paste0(encoded, collapse = "")
#> [1] "SQMYKBDUXCMDNFXQNNVYJFWKVQHMRUWPLSKTWVVKOPWPINGXJLTBZNNIPSVSFACIUJDDWARDBRGHTXDQNCDNMNOYJALNMYMWYODF"
来源：https://stackoverflow.com/questions/60332706/substitution-encryption-decryption-in-r