Replace part of strings with corresponding values from table in R

Question

I have a list of file names that encode some information as a time stamp. I would like to replace the time stamp with the appropriate corresponding information, while retaining the rest of the filename.

library(tidyverse)
filenames = c("Depth (01OCT2025 02 00 00).Terrain_2022_PartLevee.Inputs.tif", "Depth (01OCT2025 03 00 00).Terrain_2022_PartLevee.Inputs.tif", "Shear Stress (01OCT2025 02 00 00).Terrain_2022_PartLevee.Inputs.tif", "Shear Stress (01OCT2025 10 00 00).Terrain_2022_PartLevee.Inputs.tif",  "Velocity (01OCT2025 02 00 00).Terrain_2022_PartLevee.Inputs.tif", "Velocity (01OCT2025 06 00 00).Terrain_2022_PartLevee.Inputs.tif"  )

from = c("(01OCT2025 02 00 00)", 
         "(01OCT2025 06 00 00)", 
         "(01OCT2025 10 00 00)", 
         "(01OCT2025 14 00 00)"
)

to = c("Q2_ 1960cfs",
       "Q10_ 4440cfs",
       "Q20_ 5150cfs",
       "Q100_ 7130cfs"
       )
key = tibble(from, to)
# A tibble: 4 × 2
  from                 to           
  <chr>                <chr>        
1 (01OCT2025 02 00 00) Q2_ 1960cfs  
2 (01OCT2025 06 00 00) Q10_ 4440cfs 
3 (01OCT2025 10 00 00) Q20_ 5150cfs 
4 (01OCT2025 14 00 00) Q100_ 7130cfs

I am looking to do something along the lines of:

str_replace_all(filenames, from, to)  # doesn't work

to end up with:

[1] "Depth Q2_ 1960cfs.Terrain_2022_PartLevee.Inputs.tif"       
[2] "Depth (01OCT2025 03 00 00).Terrain_2022_PartLevee.Inputs.tif"   ## Not in lookup table    
[3] "Shear Stress Q2_ 1960cfs.Terrain_2022_PartLevee.Inputs.tif"
[4] "Shear Stress Q20_ 5150cfs.Terrain_2022_PartLevee.Inputs.tif"
[5] "Velocity Q2_ 1960cfs.Terrain_2022_PartLevee.Inputs.tif"    
[6] "Velocity Q10_ 4440cfs.Terrain_2022_PartLevee.Inputs.tif"

I could pull the filename vector into a table, split the string into components, left_join() with the replacement table, and recombine back into a file name, but seems like a bit cumbersome.

G. Grothendieck · Accepted Answer · 2025-10-02 11:24:23Z

5

Here are a few ways:

library(stringr)
result1 <- str_replace_all(filenames, fixed(setNames(to, from)))
identical(result1, expected)
## [1] TRUE

library(gsubfn)
result2 <- gsubfn("\\(.*\\)", setNames(as.list(to), from), filenames)
identical(result2, expected)
## [1] TRUE

library(mgsub)
result3 <- mgsub(filenames, from, to, fixed = TRUE)
identical(result3, expected)
## [1] TRUE

library(purrr)
result4 <- reduce2(from, to, ~sub(..2, ..3, ..1, fixed = TRUE), .init = filenames)
identical(result4, expected)
## [1] TRUE

Note

from <- c("(01OCT2025 02 00 00)", "(01OCT2025 06 00 00)", "(01OCT2025 10 00 00)", 
  "(01OCT2025 14 00 00)")

to <- c("Q2_ 1960cfs", "Q10_ 4440cfs", "Q20_ 5150cfs", "Q100_ 7130cfs"

filenames <- c("Depth (01OCT2025 02 00 00).Terrain_2022_PartLevee.Inputs.tif", 
  "Depth (01OCT2025 03 00 00).Terrain_2022_PartLevee.Inputs.tif", 
  "Shear Stress (01OCT2025 02 00 00).Terrain_2022_PartLevee.Inputs.tif", 
  "Shear Stress (01OCT2025 10 00 00).Terrain_2022_PartLevee.Inputs.tif", 
  "Velocity (01OCT2025 02 00 00).Terrain_2022_PartLevee.Inputs.tif", 
  "Velocity (01OCT2025 06 00 00).Terrain_2022_PartLevee.Inputs.tif")

expected <- c("Depth Q2_ 1960cfs.Terrain_2022_PartLevee.Inputs.tif",
  "Depth (01OCT2025 03 00 00).Terrain_2022_PartLevee.Inputs.tif",
  "Shear Stress Q2_ 1960cfs.Terrain_2022_PartLevee.Inputs.tif",
  "Shear Stress Q20_ 5150cfs.Terrain_2022_PartLevee.Inputs.tif",
  "Velocity Q2_ 1960cfs.Terrain_2022_PartLevee.Inputs.tif",
  "Velocity Q10_ 4440cfs.Terrain_2022_PartLevee.Inputs.tif")

edited Oct 2 at 11:24

answered Oct 1 at 22:41

G. Grothendieck

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1 Comment

r2evans Oct 2 at 0:50

Base R, for fun: Reduce(function(vec, i) gsub(key$from[i], key$to[i], vec, fixed = TRUE), seq_along(key$from), init = filenames)

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