return number of specific element of vector based of its name

Question

I need to return number of element in vector based on vector element name. Lets say i have vector of letters:

myLetters=letters[1:26]
> myLetters
 [1] "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"

and what I intent to do is to create/find function that returns me the number of element when called for example:

myFunction(myLetters["b"])
[1] 2

myFunction(myLetters["z"])
[1]26

In summary I need a way to refer to excel columns by writing letters of a column (A,B,C later maybe even AA or further) and to get the number.

I guess you're looking for `which`: `which(myLetters == 'b')` — Jaap, Aug 20 '17 at 11:00

score 1 · Accepted Answer · answered Aug 20 '17 at 11:28

If you want to refer to excel columnnames, you could create a reference vector with all possible excel column names:

eg1 <- expand.grid(LETTERS, LETTERS)
eg2 <- expand.grid(LETTERS, LETTERS, LETTERS)
excelcols <- c(LETTERS, paste0(eg1[[2]], eg1[[1]]), paste0(paste0(eg2[[3]], eg2[[2]], eg2[[1]])))

After which you can use which:

> which(excelcols == 'A')
[1] 1
> which(excelcols == 'AB')
[1] 28
> which(excelcols == 'ABC')
[1] 731

score 0 · Answer 2 · answered Aug 20 '17 at 11:11

0

If you need to find the number of times specific letter occurs then the following should work:

myLetters = c("a","a", "b")

myFunction = function(myLetters, findLetter){
  length(which(myLetters==findLetter))
}

Let find how many times "a" occurs in myLetters:

myFunction(myLetters, "a")
# [1] 2

answered Aug 20 '17 at 11:11

Aleksandr

1,814
11
19

1

imo this is not what OP is looking for – Jaap Aug 20 '17 at 11:42
Could be. Apparently he looks for a function that returns the position not the element count. – Aleksandr Aug 20 '17 at 11:49

return number of specific element of vector based of its name

2 Answers2