Is there a clean way of converting an Excel location string (e.g. "F3" or "BG5") into an R row-column index?

Question

I have a list of xlsx comments imported into R. It is a list of lists, where one of the elements present in each comment is a string representing the comment's location in Excel. I'd like to represent that as an [X,Y] numerical index, as it would be done in R.

list_of_comments
$ :List of 2
..$ location : chr "BA5"
..$ content : chr "some content"
$ :List of 2
you get the picture

I've tried doing it the hardcoded way by creating a data.frame of predefined cell names. Based on the matching content, the index would be returned. I soon realised I don't even know how to create that into the double character territory (e.g. AA2). And even if I did, I'd be left with a massive data.frame.

Is there a smart way of converting an Excel cell location into a row-column index?

Answer 1

You can use the cellranger package which helps power readxl to help here, specifically the as.cell_addr() function:

library(cellranger)
library(dplyr)

list_of_comments <- list(list(location = "BG5", content = "abc"),
                         list(location = "AA2", content = "xyz"))


bind_rows(list_of_comments) %>%
  mutate(as.cell_addr(location, strict = FALSE) %>%
           unclass() %>%
           as_tibble())

# A tibble: 2 x 4
  location content   row   col
  <chr>    <chr>   <int> <int>
1 BG5      abc         5    59
2 AA2      xyz         2    27

Answer 2

In base R you can do:

excel <- c("F3", "BG5")

r_rows <- as.numeric(sub("^.*?(\\d+)$", "\\1", excel))
r_cols <- sapply(strsplit(sub("^(.+)\\d+$", "\\1", excel), ""), function(x) {
  val <- match(rev(x), LETTERS)
  sum(val * 26^(seq_along(val) - 1))
})

data.frame(excel = excel, r_row = r_rows, r_col = r_cols)
#>   excel r_row r_col
#> 1    F3     3     6
#> 2   BG5     5    59

Or if you want to just replace location within your list (using Ritchie's example data) you can do:

lapply(list_of_comments, function(l) {
  excel <- l$location
  r_row <- as.numeric(sub("^.*?(\\d+)$", "\\1", excel))
  r_col <- sapply(strsplit(sub("^(.+)\\d+$", "\\1", excel), ""), function(x) {
    val <- match(rev(x), LETTERS)
    sum(val * 26^(seq_along(val) - 1))
  })
  l$location <- c(row = r_row, col = r_col)
  l
})
#> [[1]]
#> [[1]]$location
#> row col 
#>   5  59 
#> 
#> [[1]]$comment
#> [1] "abc"
#> 
#> 
#> [[2]]
#> [[2]]$location
#> row col 
#>   2  27 
#> 
#> [[2]]$comment
#> [1] "xyz"

^{Created on 2022-04-06 by the reprex package (v2.0.1)}