Read files in pairs in R using regular expression

I am trying to list files in pairs in R but my way is a bit messy and I have to provide all the file names manually in pairs.

Currently I am doing like this:

files <- list(
  c("postgwas2hmp_Extr_Soil_C_Ratio_top1.txt","manhattan_Extr_Soil_C_Ratio__top1.txt"),
  c("postgwas2hmp_Extr_Soil_P_Ratio_top1.txt","manhattan_Extr_Soil_P_Ratio__top1.txt"),
  c("postgwas2hmp_Total_Soil_D_Ratio_top1.txt","manhattan_Total_Soil_D_Ratio__top1.txt"),
  c("postgwas2hmp_Extr_Soil_E_Ratio_top1.txt","manhattan_Extr_Soil_E_Ratio__top1.txt")
  )

And then I am using these files in a r function. It is working fine but is there any way I just need to reads all these files in pairs using regular expression just in one line something like this:

files <- list(
  c("postgwas2hmp_*//.txt$","^manhattan_.*\\.txt$")
  )

This second code is not working but I want something like this to avoid listing all the files individually.

And What I finally want to have after list calling:

str(files)
List of 4
 $ : chr [1:2] "postgwas2hmp_Extr_Soil_C_Ratio_top1.txt" "manhattan_Extr_Soil_C_Ratio__top1.txt"
 $ : chr [1:2] "postgwas2hmp_Extr_Soil_P_Ratio_top1.txt" "manhattan_Extr_Soil_P_Ratio__top1.txt"
 $ : chr [1:2] "postgwas2hmp_Total_Soil_D_Ratio_top1.txt" "manhattan_Total_Soil_D_Ratio__top1.txt"
 $ : chr [1:2] "postgwas2hmp_Extr_Soil_E_Ratio_top1.txt" "manhattan_Extr_Soil_E_Ratio__top1.txt"

Thanks,

If your files are all in the same directoy we can use list.files() and provide a regex pattern. This should work (given the files are in your working directory). Below I put the following two files in my current working directory: "postgwas2hmp_Extr_Soil_C_Ratio_top1.txt" and "manhattan_Extr_Soil_C_Ratio__top1.txt". Then the result of list.files() is as follows:

list.files(pattern = "^(manhattan|postgwas2hmp)_.*\\.txt$")
#> [1] "manhattan_Extr_Soil_C_Ratio__top1.txt"  
#> [2] "postgwas2hmp_Extr_Soil_C_Ratio_top1.txt"

To generate a list with two elements containing the same letter we can use the following approach:

x <- list.files(pattern = "^(manhattan|postgwas2hmp)_Extr_Soil_.*\\.txt$")

letrs <- unique(gsub("^(manhattan|postgwas2hmp)_Extr_Soil_([A-z]+).*", "\", x))

lapply(letrs,
       \(x) list.files(pattern = paste0("^(manhattan|postgwas2hmp)_Extr_Soil_", x, "_.*\\.txt$"))
       )

#> [[1]]
#> [1] "manhattan_Extr_Soil_B_Ratio__top1.txt"  
#> [2] "postgwas2hmp_Extr_Soil_B_Ratio_top1.txt"
#> 
#> [[2]]
#> [1] "manhattan_Extr_Soil_C_Ratio__top1.txt"  
#> [2] "postgwas2hmp_Extr_Soil_C_Ratio_top1.txt"

^{Created on 2023-02-24 by the reprex package (v2.0.1)}

My approach would be to split out the components of your file names, assemble them and then create the lists. The final manipulation of the lists uses a pivot_wider() and then some playing around with the names to clean them up. This may not be needed.

library(tidyr)
library(dplyr)

topic <- c("postgwas2hmp_", "manhattan_")
id <- c("Extr_Soil_C", "Extr_Soil_P", "Total_Soil_D", "Extr_Soil_E")
run <- c("Ratio_top1", "Ratio_top1")
end <- c(".txt")

df <- crossing(topic, id, run, end) %>% 
  mutate(files = paste0(topic, id, run, end)) %>% 
  as_tibble() %>% 
  pivot_wider(names_from = topic, values_from = files) %>% 
  select(-c(id, run, end)) 

df <- df %>% 
  unlist() %>% 
  unname() %>% 
  split(f = seq(nrow(df))) %>% 
  unname()

[[1]]
[1] "manhattan_Extr_Soil_CRatio_top1.txt"    "postgwas2hmp_Extr_Soil_CRatio_top1.txt"

[[2]]
[1] "manhattan_Extr_Soil_ERatio_top1.txt"    "postgwas2hmp_Extr_Soil_ERatio_top1.txt"

[[3]]
[1] "manhattan_Extr_Soil_PRatio_top1.txt"    "postgwas2hmp_Extr_Soil_PRatio_top1.txt"

[[4]]
[1] "manhattan_Total_Soil_DRatio_top1.txt"    "postgwas2hmp_Total_Soil_DRatio_top1.txt"