read.table faster with known column classes and data.table::fread. I wonder which one is

readTableFast.R

.readTableFast<-function(filename,header=T,skip=0,sep="")
{
  tab5rows <- read.table(filename, header = header,skip=skip,sep=sep, 
                         nrows = 100,stringsAsFactors=FALSE)
  classes  <- sapply(tab5rows, class)
  classes[classes=="logical"]="character"
  return( read.table(filename, header = header,skip=skip,sep=sep, 
                     colClasses = classes)  )
}

require(data.table)
.readTableFast2<-function(filename,header=T,skip=0,sep="")
{
  # probably no need for these lines as they don't seem to 
  # improve fread performance
  tab5rows <- read.table(filename, header = header,skip=skip,sep=sep, 
                         nrows = 100,stringsAsFactors=FALSE)
  classes  <- sapply(tab5rows, class)
  classes[classes=="logical"]="character"
  
  
  return( fread(filename, header = header,skip=skip,sep=sep, 
                     colClasses = classes)  )
}