text: # Author: joelowj
  # License: Apache License, Version 2.0
  
  import pandas as pd
  
  
  def rocr(df, price, rocr, n):
      """
      The Rate-of-Change Ratio (ROCR) indicator, which is also referred to as simply
      Momentum, is a pure momentum oscillator that measures the percent change in
      price from one period to the next.
  
      Parameters:
          df (pd.DataFrame): DataFrame which contain the asset information.
          price (string): the column name of the price of the asset.
          rocr (string): the column name for the rate of change ratio.
          n (int): the total number of periods.
  
      Returns:
          df (pd.DataFrame): Dataframe with rocr of the asset calculated.
  
      """
  
      df[rocr] = df[price] / df[price].shift(n)
      df = df.dropna().reset_index(drop=True)
  
      return df
  