CODEWITHSUNDEEP
rloopsdataframe
TMS
TMS

Reputation: 3

R Use variable as dataframe name and then access dataframe

I have the following code which goes through a list of files in folder and reads each into a data frame which is named based on the original file name:

myfiles = list.files(pattern="*.avg")
for (file in myfiles){
    dataname = paste("S",gsub("_","",gsub("\\.avg", "", file)), sep = "")
    assign(dataname, read.table(file, header = FALSE, col.names = c("wl","ref","sd")))
}

My problem is that once I have the 100 dataframes read into R, I cannot then access them directly using the variable dataname as this is a character string e.g "dataframe1".... I wish to have a further few statements within the loop to process each dataframe and hence need to access the dataframe. Any ideas on how I can do this?

Upvotes: 0

Views: 2065

Answers (1)

eipi10
eipi10

Reputation: 93871

Expanding on @arvi1000's suggestion, you can just read the files directly into a list:

myfiles = list.files(pattern="*.avg")
file.list = sapply(myfiles, read.table, header=FALSE, col.names=c("wl","ref","sd"))

Now each element of the list is a data frame and the name of each element of the list is the name of the file that was the origin of the data frame stored in that list element.

If you want to process each file, you can also do that within sapply. For example:

file.list = sapply(myfiles, function(file.name) {
  df = read.table(file.name, header=FALSE, col.names=c("wl","ref","sd"))
  df$file.name = file.name  # Add name of origin file as a new column
  ... additional data frame processing statements ...
  })

The idea is that you just do all the data cleaning/processing, etc. that you want and then each cleaned/processed data frame will be an element of the list. In the example above, I added a column with the name of the file that a given data frame came from. This might be useful if you wanted to combine all of your data frames into a single data frame, but to be able to tell which file a given row came from. In that case, after reading the data frames into a list, you could then combine them into a single data frame as follows:

my_df = do.call(rbind, file.list)

Upvotes: 3

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