code: def calculateFirstDifference(filePath, outputFilePath):
      
      predictedField = SWARM_CONFIG['inferenceArgs']['predictedField']
  
      data = pd.read_csv(filePath, header=0, skiprows=[1,2])
      predictedFieldVals = data[predictedField].astype('float')
      firstDifference = predictedFieldVals.diff()
      data[predictedField] = firstDifference
  
      inputFile = open(filePath, "r")
      outputFile = open(outputFilePath, "w")
      csvReader = csv.reader(inputFile)
      csvWriter = csv.writer(outputFile)
      # write headlines
      for _ in xrange(3):
        readrow = csvReader.next()
        csvWriter.writerow(readrow)
      for i in xrange(len(data)):
        csvWriter.writerow(list(data.iloc[i]))
  
      inputFile.close()
      outputFile.close()
docs: Create an auxiliary data file that contains first difference of the predicted field
      :param filePath: path of the original data file