为什么我在进行预测时从 ARIMA 模型得到几乎相同的结果？

Question

I've been changing the AR and MA coefficients but still the same..so this is my code :

model = ARIMA(df, order =(4,0,4))
results_ARIMA = model.fit(disp=0)
print(results_ARIMA.summary())
n = 520
result = results_ARIMA.forecast(steps=n+1)[0]
result.head()

array([ 41.95623053,  41.98185411,  41.89815634,  41.94481325,
        41.87636322,  41.89761647,  41.82752735,  41.87473589,
        41.80196085,  41.82483214,  41.76732314,  41.80917335,
        41.73434308,  41.76354033,  41.71405822,  41.74715261,
        41.67522211,  41.71211599,  41.66466619,  41.68942922,
        41.62553526,  41.66771581,  41.61747084,  41.63769232,
        41.58473465,  41.6272783 ,  41.57252176,  41.59344323,
        41.55081621,  41.58859627,  41.53118001,  41.55706031,
        41.52102605,  41.55097806,  41.49517932,  41.52744945,
        41.49288592,  41.51522557,  41.46560754,  41.50239611,
        41.46506061,  41.48297757,  41.44226148,  41.47941698,
        41.43768935,  41.45574504,  41.42363582,  41.45670059,
        41.41206449,  41.43408257,  41.40750963,  41.43371217,
        41.38983724,  41.41725247,  41.39183213,  41.41121285,
        41.37212952,  41.40349845,  41.37549464,  41.39071864,
        41.35894938,  41.39076871,  41.35865194,  41.37367136,
        41.34914894,  41.37753874,  41.34247627,  41.36070523,
        41.34090922,  41.36336173,  41.32848649,  41.35132692,
…

Answer 1

Model is taking average of your historical data and predicting the future. If you plot the data you will get stright line. This happens when your historical data does not have strong seasonality therefore model takes average of previous values and predict future data points.( in short its difficult for a model to predict with good accuracy with out strong seasonality) Hope answer to your question.