select files from a list of files with a pattern

Question

I have a list of files, which was created using list.files:

filesxx<-list.files(pattern="0-4000")

obtainig a list like the following one:

  [1] "Alta Guajira Coord & elevation TS 0-4000.txt"     "Baja Guajira Coord           & elevation TS 0-4000.txt"    
  [3] "Bajo Meta Coord & elevation TS 0-4000.txt"        "Rio Arauca Coord & elevation TS 0-4000.txt"      
  [5] "Rio Catatubo Coord & elevation TS 0-4000.txt"     "Rio Cesar Coord & elevation TS 0-4000.txt"       
  [7] "Rio Sogamoso Coord & elevation TS 0-4000.txt"     "Rio Tomo Coord & elevation TS 0-4000.txt"        
  [9] "Sabana de Bogota Coord & elevation TS 0-4000.txt" "Total Area Coord & elevation TS 0-4000.txt"

and from this list I want create a loop that will select one of this files depending on the loop variable (a) wich will be a pattern in the name, for example the variable (a) will be: "Alta Guajira" and in the next cycle "Rio Tomo".. etc

How can I do this, how to chose a file with a pattern from a list of files already made? I think the function Shopt is more to exclude patterns and maybe the function find could work but after looking for some similar case I havent found the answer.

Where/what is the pattern between `Alta Guajira`and `Rio Tomo`, it does not seem apparent. — Gin_Salmon, May 16 '17 at 11:53
Are your pattern always consecutive strings in the name? If so, use `grep()`. — LAP, May 16 '17 at 11:56
I think it was not clear so I edited the question, the list was created using list.files and from this list I will use the loop and the loop variable will be the "new pattern" and will change in every cycle but I dont know how to look for a pattern in a list which is already a list.files result. I hope its clear the question — Davido, May 16 '17 at 12:42
@Gin_Salmon "Alta Guajira", "Rio Tomo".. etc are elements in a vector that the loop variable will take in every cycle to chose one of this files, but this list that i show is already a result of using list.files with an initial pattern: "0-4000". Now I need a method to filter from this list with a pattern that changes every cycle — Davido, May 16 '17 at 12:49

KenHBS · Accepted Answer · 2017-05-16T13:02:13.077

You can list the files in your working directory with list.files(). It has an argument allowing you to specify a certain pattern:

 list.files(pattern = "Alta Guajira")
 # [1] "Alta Guajira Coord & elevation TS 0-4000.txt"

If you have a vector with the patterns in there, like:

patterns <- c("Alta Guajira", "Rio Tomo", "Rio Sogamoso")
sapply(patterns, function(x){list.files(pattern = x)})

Edit

If you already have the file names, you are basically looking for patterns in a character vector.

df <- c("Alta Guajira Coord & elevation TS 0-4000.txt","Baja Guajira Coord & elevation TS 0-4000.txt", 
        "Bajo Meta Coord & elevation TS 0-4000.txt", "Rio Arauca Coord & elevation TS 0-4000.txt",
        "Rio Catatubo Coord & elevation TS 0-4000.txt", "Rio Cesar Coord & elevation TS 0-4000.txt",
        "Rio Sogamoso Coord & elevation TS 0-4000.txt", "Rio Tomo Coord & elevation TS 0-4000.txt",
        "Sabana de Bogota Coord & elevation TS 0-4000.txt", "Total Area Coord & elevation TS 0-4000.txt")

patterns <- c("Alta Guajira", "Rio Tomo", "Rio Sogamoso")

it  <- 0
res <- c()
for(i in patterns){
    it  <- it + 1
    res <- append(res, df[grepl(pattern = i, x = df)])
}
res
# [1] "Alta Guajira Coord & elevation TS 0-4000.txt" "Rio Tomo Coord & elevation TS 0-4000.txt"    
# [3] "Rio Sogamoso Coord & elevation TS 0-4000.txt"

Or, alternatively:

res2 <- sapply(patterns, function(y){df[grepl(pattern = y, x = df)]})

I was able to adapt your answer, it works fine now. Thanks! – Davido May 16 '17 at 13:18 — Davido, May 16 '17 at 13:18

select files from a list of files with a pattern

1 Answers1

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