cell_limit to vector of cell references

[alephreish]

What is the recommended way of obtaining a vector of individual cell references from a cell_limit object? When dealing with columns < AA (which is my case since I'm actually parsing coordinates on A1:H12 PCR plates), one can do:

cl <- as.cell_limits("R1C1:R1C9")
eg <- expand.grid(LETTERS[cl$ul[2]:cl$lr[2]], cl$ul[1]:cl$lr[1])
paste0(eg[[1]], eg[[2]])
# [1] "A1" "B1" "C1" "D1" "E1" "F1" "G1" "H1" "I1"

Is there a lightweight generic solution?

[nacnudus]

I did something similar recently, using cellranger::to_string() to handle columns > AA, and would have made a PR for unrange(), but for two things:

• How to handle the 'whole column' and 'whole row' case, e.g. A:A and 4:4.
• A dplyr-like set of join functions might meet the use-case better, i.e. a kind of spatial join of cells to cells, cells to ranges, ranges to cells, and ranges to ranges.

Anyway, this was the code.

unrange <- function(x) {
  limits <- cellranger::as.cell_limits(x)
  rows <- seq(limits$ul[1], limits$lr[1])
  cols <- seq(limits$ul[2], limits$lr[2])
  rowcol <- expand.grid(rows, cols)
  cell_addrs <- cellranger::cell_addr(rowcol[[1]], rowcol[[2]])
  cellranger::to_string(cell_addrs, fo = "A1", strict = FALSE)
}

unrange("A121:A122")
#> [1] "A121" "A122"

[alephreish]

Looks nice despite the shortcomings. Do make a PR!

[jennybc]

I note you can also do this:

reprex::reprex_info()
#> Created by the reprex package v0.1.1.9000 on 2017-10-24

library(magrittr)
library(cellranger)

cell_addr(1, 1:9) %>% 
  to_string(fo = "A1", strict = FALSE)
#> [1] "A1" "B1" "C1" "D1" "E1" "F1" "G1" "H1" "I1"

I haven't looked at the package in a long time! The cell_addr class (and the ra_ref class) are from an unfinished effort to setup some classes useful for formula parsing down the road. It's all a bit foggy in my mind right now.

But I agree, it seems like there's some missing piece here that would be useful.

[nacnudus]

That's neat. It works on single-row or single-column ranges, but for rectangles expand.grid() is still needed.

library(magrittr)
library(cellranger)

cell_addr(1:2, 1:9) %>%
  to_string(fo = "A1", strict = FALSE)
#> Error: length(row) == length(col) is not TRUE

@jennybc if you get a chance to revisit those ideas, I'd love to hear more.