loader.r

loadMNISTData <- function(dataFilename, labelFilename) {
  # Loads the data from the MNIST dataset. The data can be downloaded from:
  # http://yann.lecun.com/exdb/mnist/

  # Args:
  # dataFilename: specifies the name of the file containing the data
  # labelFilename: specifies the name of the file containing the labels

  # Returns:
  # The data and the labels combined in a list data structure

  dataFileIn = file(dataFilename, "rb")
  # read the first unsigned byte
  dummyByte = readBin(dataFileIn, integer(), n = 1, size = 4, endian = "big")
  if (dummyByte != 2051) {
    stop("Error reading file.")
  }
  # read the number of data
  nData = readBin(dataFileIn, integer(), n = 1, size = 4, endian = "big")
  x <- readBin(dataFileIn, integer(), n = 1, size = 4, endian = "big")
  y <- readBin(dataFileIn, integer(), n = 1, size = 4, endian = "big")
  dataSize = x * y
  data <- matrix(data = 0, nrow = nData, ncol = dataSize)
  for (i in 1:nData) {
    data[i,] <- readBin(dataFileIn, integer(), n = dataSize, size = 1,
                        endian = "big", signed = FALSE)
  }
  close(dataFileIn)

  # read the labels
  dataFileIn = file(labelFilename, "rb")
  # read the first unsigned byte
  dummy_byte = readBin(dataFileIn, integer(), n = 1, size = 4, endian = "big")
  if (dummy_byte != 2049) {
    stop("Error reading file")
  }
  # read the number of data
  nData = readBin(dataFileIn, integer(), n = 1, size = 4, endian = "big")
  dataSize = 1
  labels <- matrix(data = 0, nrow = nData, ncol = dataSize)
  for (i in 1:nData) {
    labels[i] <- readBin(dataFileIn, integer(), n = 1, size = 1, endian = "big", signed = FALSE)
  }
  close(dataFileIn)

  return(list("data" = data, "labels" = labels))
}