Get the numbers (indices) corresponding to alphabetical colnames

This function supports nchar up to 4, i.e. from "A" to "ZZZZ".

abc2index(abc)

Arguments

abc

a character vector to be converted to numbers (indices).

Value

an integer vector

Examples

abc2index(letters)         # 1–26
#>  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
#> [26] 26
abc2index(c("a", NA, "a")) # 1 NA 1
#> [1]  1 NA  1
if (FALSE) {
 abc2index("zzzza")         # Error
}