_next_observation method might be looking into the future

[renatodvc]

Hello,
I'm still getting acquainted with OpenAI Gym, so I'm not entirely sure about this issue, but it's possible that for each step, the _next_observation method is sending the next (future) 5 candles information, instead of the last five candles.

    def _next_observation(self):
        # Get the stock data points for the last 5 days and scale to between 0-1
        frame = np.array([
            self.df.loc[self.current_step: self.current_step +
                        5, 'Open'].values / MAX_SHARE_PRICE,
            self.df.loc[self.current_step: self.current_step +
                        5, 'High'].values / MAX_SHARE_PRICE,
            self.df.loc[self.current_step: self.current_step +
                        5, 'Low'].values / MAX_SHARE_PRICE,
            self.df.loc[self.current_step: self.current_step +
                        5, 'Close'].values / MAX_SHARE_PRICE,
            self.df.loc[self.current_step: self.current_step +
                        5, 'Volume'].values / MAX_NUM_SHARES,
        ])

This is the first 6 days of the dataframe (AAPL.csv):

Index	Date	Open	High	Low	Close	Volume
0	1998-01-02	13.63	16.25	13.50	16.25	6411700.0
1	1998-01-05	16.50	16.56	15.19	15.88	5820300.0
2	1998-01-06	15.94	20.00	14.75	18.94	16182800.0
3	1998-01-07	18.81	19.00	17.31	17.50	9300200.0
4	1998-01-08	17.44	18.62	16.94	18.19	6910900.0
5	1998-01-09	18.12	19.37	17.50	18.19	7915600.0

Setting the self.current_step to 0, and printing the frame array:

[[0.002726, 0.0033, 0.003188, 0.003762, 0.003488, 0.003624], 
[0.00325, 0.003312, 0.004, 0.0038, 0.003724, 0.003874],
[0.0027, 0.003038, 0.00295, 0.003462, 0.003388, 0.0035],
[0.00325, 0.003176, 0.003788, 0.0035, 0.003638, 0.003638],
[0.00298568, 0.00271029, 0.0075357, 0.00433074, 0.00321814, 0.00368599]])

If we remove the normalization:

[13.63, 16.5,  15.94, 18.81, 17.44, 18.12] #Open
[16.25, 16.56, 20. , 19. , 18.62, 19.37] #High
[13.5,  15.19, 14.75, 17.31, 16.94, 17.5] #Low
[16.25, 15.88, 18.94, 17.5,  18.19, 18.19] #Close
[ 6411700. , 5820300. , 16182800. , 9300200. , 6910900. , 7915600. ] #Volume

If you check the DF you will see that those are the next 5 future prices/volume for the next steps. Logic applies to all following steps as well, not limited to step 0.