如何将函数参数传递给map_df（）？

Question

I am trying to create a function to clean data and return as a data.frame in R.

I'm using the map_df() function to return the cleaned data as a data.frame, and have a function written to clean the data.

The first thing I do is pull a list of files from a folder, then iterate through them and clean each file. I have a pre-defined set specifying which column names to pull (stored in selectCols) in case of variation between files:

files <- list.files(filepath,full.names=F)
colInd <- which(names(fread(files[i],nrows=0)) %in% gsub("_","",selectCols))

I also have a function to clean my data, which uses fread() to read in the .csv files. It takes colInd and i as arguments to clean files iteratively.

cleanData <- function(files,i,colInd) {
    addData <- fread(files[i],select=c(colInd))
    [...]
}

Overall it looks like this (as a recursive function):

i <- 1
files <- list.files(filepath,full.names=F)

iterateCleaning <- function(files,i) {
    colInd <- (which(names(fread(files[i],nrows=0)) %in% gsubs("_","",selectCols))

    if (length(colInd)==length(selectCols)) {
        newData <- map_df(files,cleanData)
        saveToFolder(newData,i,files)
    }
    else {}

    i=i+1

    if (i<-length(files)){
        iterateCleaning(files,i)
    }
    else {}
}

When I try to run without specifying the arguments for my function I get this error:

Error in fread(files,select=c(colInd)): 
    argument "colInd" is missing, with no default.

When I insert it into my map_df() I do it like so:

newData <- map_df(files,i,colInd,cleanData)

Then I get this error:

Error in as_mapper(.f,...): object 'colInd' not found.

Any suggestions for resolving this error? As I understand it, map_df() applies to each element in the function, but I don't need it applied to the i and colInd inputs, I just need them for the function I am calling in map_df(). How can I call map_df() on a function that requires additional arguments?

I read the documentation but it seemed a bit confusing. It says for a single-argument function to use "." and for two-argument functions to use .x and .y, but I'm not sure what it means. My initial guess is something like these, but neither line works):

newData <- map_df(files,cleanData,.i,.colInd)

newData <- map_df(files,cleanData,.x=i,.y=colInd)

Any recommendations? Will I have the same output if I just call map_df() afterwards on the output of my function?