SavingFiles

participant <- 1:30
tasks <- c('a','b','c')
session <- 1:20

# Make sure our folder exists for saving into.
baseDir <- './AllTheFiles/'
if (!dir.exists(baseDir)) {dir.create(baseDir)}

# Here is a pretty traditional computer-languagy way to do it:
for (p in participant) {
  for (tsk in tasks) {
    for (s in session) {
      # This step just generates random data to write.
      currentDf <- data.frame(
        rndNum1 = rnorm(10),
        rndNum2 = runif(10)
      )

      # Construct a different file name for each case.
      flNm <- paste(p, tsk, s, sep = "_")
      # Write the file. Note the paste0() statement, which ensures that the
      # files end up in a folder called "AllTheFiles" (in the current working
      # directory). It also adds the txt file extension.
      write.table(
        currentDf,
        file = paste0(baseDir, flNm, ".txt")
      )
    }
  }
}

# A slightly more R-y way to do it
combos <- expand.grid(participant, tasks, session, stringsAsFactors = F)

apply(combos, MARGIN = 1, function (combo) {
    # This code is the same as in the for-loop way, but referencing the combos
    # object instead of looping directly on the original objects.
    p <- combo[1]
    tsk <- combo[2]
    s <- combo[3]

    currentDf <- data.frame(
      rndNum1 = rnorm(10),
      rndNum2 = runif(10)
    )
    flNm <- paste(p, tsk, s, sep = "_")
    write.table(
      currentDf,
      file = paste0(baseDir, flNm, ".txt")
    )
  }
)