Subset String by Position of Characters in R-CodePudding

I can't seem to find an elegant solution to a relatively simple problem in R. I would like to extract characters from a string based on a vector of positions. For example, how could I extract the 1st, 3rd, and 5th characters from example.string? substr does not work without a beginning and end.

example.string <- "ApplesAndCookies"
characters.wanted <- c(1,3,5)

Expected output would be: Ape

I can design a loop or function to do this, but there has to be an easier way...

CodePudding user response：

A possible solution for a single string.

example.string <- "ApplesAndCookies"
characters.wanted <- c(1,3,5)

paste(unlist(strsplit(example.string, ''))[characters.wanted], collapse = '')
# ---------------------------------------------------------------------------
[1] "Ape"

Extension to a vector of strings.

example.string <- c("ApplesAndCookies","ApplesAndCookies","ApplesAndCookies")
characters.wanted <- c(1,3,5)

sapply(strsplit(example.string, ''), function(x) {
  paste(x[characters.wanted], collapse = '')
})
# ---------------------------------------------------------------------------
[1] "Ape" "Ape" "Ape"

CodePudding user response：

For a single string and a single vector you can

rawToChar(charToRaw(example.string)[characters.wanted])

Output

[1] "Ape"

CodePudding user response：

You could use:

example.string <- "ApplesAndCookies"
characters.wanted <- c(1,3,5)

paste(strsplit(example.string, "")[[1]][characters.wanted], collapse="")

Output:

[1] "Ape"